Reposted this lower down, as about a million replies since my edit
Right, so far I've resisted the urge to post here and slam it like all you lot have I've played it fairly extensively online and offline in all the cars on all the tracks.
First Thoughts
What a horrid way of designing a modern sim, with a separate VB interface. Nothing is easy, and there are exceptionally few options to tailor the sim to your tastes or computer. But I managed to licence myself, and select car skins etc. The multiplayer lobby is a joke really, even with the much improved patch. You can't filter anything, not even full/private/empty etc, and you can't tell if a server is passworded til you've spent a minute loading the sim program. Neither can you join a server unless it's in a very specific join period which is just annoying a stupid. I can understand not allowing people to just drive on track, but to not allow them to join (but allow them to try) is just stuuuuupid
AIM
I was hoping this bit would be cool. and in a way it is. But it's almost impossible to use, and at the resolution I have to use (aging PC) and FOV I like (80) I can barely read anything. But the shift lights are very nice, especially how they flash. None of this perfect shift point light like in LFS. Trouble is you can't configure the shift points to the correct revs for a given ratio as you can't see the torque curve and wheel sizes are unknown I think (though I bet you can work them out from telemetry). And it's stupid to completely disable it in the demo (not including the workaround) - people need to see the revs and gear they're in, at the very least...
Graphics
Some seriously nice touches in there in my opinion. The tracks are nicely lit, and the textures are generally top notch. But at no point have I been convinced that the cars are on the track - they ALWAYS look like the cars have been photoshopped into the scene, perhaps because the cars are subjected to different lighting, or the car shadows not working with the track appearence. Nice touches I've noticed are the smoke, the reflective pit wall windows, and the pit garage, which looks a bit 'lived in'. The car models themselves seem excellent, especially the cockpits.
Sound
Woahhh, BEES (see attachment). Whilst the sound engine is VERY good in some respects - the low speed hunting at full throttle, the exhaust crackling on the overrun and the starter sounds - the actual sound generated is just rubbish. Much worse than LFS S1's. But it has potential in that area.
Driving
Driving out of the pits, it all feels nice. The cars are clearly attached to the ground, rather than floating above it a la rFactor. You can floor it, control the wheelspin, and generally chuck it around without it having 'too much' grip faked, a la 99% of other sims (not inc. LFS). It was nice to just get out and drive. I didn't have problems starting the car, although the hidden button on the FTarget did confuse me for a minute or two. Gear changing is silly. Whilst it's undoubtedly the 'correct' way of changing gear for the cars, it doesn't work in a sim. In a real formula car, even with nancy throttle cuts levers and stuff, you get feedback from EVREYTHING to help you shift. I'd bet REAL money that a real car is easier to shift than the F1600/1800. But once I found that two quick upshift requests resulted in a shift it was okay. So I accelerated towards the first corner and braked. Nothing special here, the car slowed I went round the corner and accelerated out. Hmmmm, easy. A few laps later, after my confidence had increased (and a few crashes later too), I was braking later, turning more aggresively (depsite my Early Turn In driving style), and getting on the throttle earlier. Can jump on the throttle most of the time, and if it's too much you can just about feel that the back end is going to come round and you can correct it, just about. But occasionally, braking in exactly the same way as before, the back will swing out 90 degrees (almost without exception it's 90 degrees), which isn't right I don't think. Maybe my manual blipping isn't perfect in sims yet, but it didn't feel like it was related to that... Plenty (perhaps too much) understeer in corners, especially with the non-downforce cars.
I was also impressed by the tyre temp modelling. Do a burnout and the understeer is worse by about the right amount (cold fronts). Weave to warm the fronts and oversteer is very much a problem. But they don't lose enough grip after a 3 minute burnout in my opinion.
Flatspotting. I quite like the shaky FFB once I've locked up, but it's just too much. I'm really concerned about the life of my wheel with that vibration, even from a relatively little lock up. And I have no idea if it's a rear or a front I've locked.
Mirrors - why are they always dirty round the edges? And why can't I see my rear tyres? Surely if the tyre condition is done visually I need to see them, just like you can in a real formula car (F1 and my F3 anyway).
Damage
I loved the idea of wheel tethers. I really did. But OMG, they do such funny things. Flapping around COMPLETELY unrealistically. And the 'floor on track' noise is sooooo loud compared to all the other sounds - poor speakers. Wings can be knocked off (though no apparent damage, just no wing), tie rods and track rods can be bent (is it visually, not checked). But the cars a touch too fragile. I've seen real Fford racing, and they DO bang wheels without instant suspension damage. Shame no sim has the wheel-wheel contact flipping modelled though...
I thought I'd also love the idea of repairs taking time, but it's really irritating. Sure, it might be more acceptable in a league race, but I found myself disconnecting and rejoining to repair the car. And if you alter your wing by one stop, you have to wait 10 minutes. Now I'm not an F1 mechanic, but I can adjust my F3's rear wing in about a minute, if that. Nice idea, poorly implemented.
The tyre wear/condition being remembered between sessions is also something I thought was going to be brilliant. But it isn't. I've no idea what condition my tyres are in (is 18km good?), and if you forget you can find yourself in a race with very very bad tyres. And what's the other tyre type for in the F2000? I think it would be great to have a number of tyres for a weekend (practice/qually/race), and to be able to inspect them, and no information about them, but nK doesn't give you any of this. So now I just mount new tyres every time I leave the pits. Can you ever run out? I haven't yet!
But isn't it nice to run over the grass and see it on your (front) tyres, and then see it wear off. Shame it doesn't [seem to] affect grip at all, but it's a lovely feature, and I can't wait for it to be in LFS (which it surely will be one day).
Immersion
Sometimes it's brilliant. Other times it's pants. The tracks are poor in terms of design, they are all very similar and featureless. The only corner I really enjoy is the last one at Newbury, where the exit is VERY close to the wall. But it's hard to learn the tracks without some form of keypoints, which is something our Eric is very good at.
Clutch and Engine
Deserves a whole section to itself. I love stalling. It feels so good to not use quite enough revs, or to not dip the clutch/keep the revs up after a spin and stall. It's something LFS really does need now I've tried it. Even with auto-clutch (no clutch pedal on these ECCI babies) it stalls if you don't use enough revs or do the right thing. And I like having to manually blip/lift the throttle. Whilst I would use it in LFS, the speed/consistency advantage with having it is too great an incentive - get rid of the options in LFS and I'll be happier.
Too high a gear at too low a speed - the car shudders and shakes, just like in real life. Another brilliant addition that adds to the (otherwise weak) immersion.
Force Feedback
Um, yeah. Not sure what's going on. For starters you have NO CONTROL over the strenth in the UI (have to edit ini files), and even then I can't make the linear/exponent thingy do anything - is that FFB related or is it wheel turn compensation (to all intents)?
Sometimes the FFB is brilliant. I'm loving driving over serrated kerbs and feeling it. But I can't feel understeer (maybe I'm setting it up wrong as some people say they can). I can just about feel oversteer. I can't tell if I've locked up or if I'm going to fast. And then sometimes it just turns off, so I get even less than before. But at least it's not canned (I think), and is MILES better than rF/GTR/GTL/GPL/GT4. But it does shake you around a bit, and feel more alive - LFS is a bit dead in this regard.
Misc
The track signs (100m, 50m) are better than LFS's in so much as hitting them DOESN'T create a massive crash. But they've gone too far so now you don't fear hitting them at all. And the animation as they break looks very fake too.
How do you get into the pits - I end up going forwards and backwards outside the pit garage to try and find the sweetstop that allows you to do anything. Then I find you can't do anything, so I just pit to the garage.
What the hell does Disconnect do in the Esc menu. Doesn't disconnect you online at all that I can see
It crashes. A lot. Or, if it doesn't crash it justs in to a huff and does rude things out of spite
Can't send setups online? WTF. Even rFactor added this, and rFactors worse! I can understand skins not being auto-downloaded (we are, of course, spoilt in LFS), but not setups? Now I have to give my email address out, leave the sim, copy it into the right place, load it, and try to reconnect. Hardly streamlined.
Look left/right in cockpit. Sudden movements? How annoying is that - you lose all sense of direction and speed. Needs a smooth movement like, well, every other sim I can think of.
The lack of information is disturbing. I like not having overlays, but a simulation NEEDS some, even if it's only an interface thing like F12 in LFS rather than a 'we'll show you this so you beleive with model it' overlay like F9.
No free camera?
Doom mode - I'm sure Stefano said it would be ASDW controls like a modern FPS. But no, we get arrows (just up and down), a crouch key, and the ability to walk through walls. Nice idea, but as it is it's useless. I can't tell the difference between 1 and 1.5 degree of camber on my competitors cars, so why bother. If we could see other drivers, and actually do something useful (or see something useful like times, or damage notes, or SOMETHING) then it might be a nice feature. Until then I'll stick with Teamspeak (though I would like a voIP client built in).
So, in summary I think nK has awesome potential. In a few months it'll be amazing compared to what it is now. But unfortunately, for nK, it's not as good as LFS at the moment, and by the time the nK patches come along LFS with have moved further ahead. I really enjoyed the thought of nKP. I honestly thought it was going to kick LFS in the nuts and run off giggling. But it hasn't, not by a long shot. I've since played some LFS (LX4 @ SO4r) with Anton and it's so much better. You really feel like you are controlling a several hundred kg car. You can feel the car squirming, you can tell if you've snatched a wheel (even without sounds sometimes). As a driving simulator LFS is a Space Shuttle to nK's Wright Flyer. But nK is by no means awful. It's EASILY the 2nd best simulator on the market today, and I look forward to future patches, additions and devkits. I won't be uninstalling it, but it won't be replacing LFS as my first love (apologies to the missus if she reads this). And it's definitely shown LFS a few tricks, which no doubt LFS will better very soon. Perhaps Stefano needs a week of LFS to show him what to do...
I've almost certainly missed something(s) off here, and it's by no means my final opinion. I need another week or two to really get my head around these physics, as it DOES take a while to acclimatise. It won't be as good as LFS in two weeks (patches not withstanding, for either sim), but it does have a very real and fair place next to LFS. And competition, even if it's only weak at this stage, is good for both teams.