I have been part of iracing for about a year and a half now, maybe two - I can't remember (class A now, thank you), and as the original post said: It's
alot more serious.
They don't call it a game, it's a simulation, and for good reason! When you have major racers joining sessions regularly, you know you've done something special. I have raced with the likes of Earnhardt Jr and Allmendinger (and maybe a few from street racing, but I don't know many names from any of those series). When you finish in front of them, it doesn't feel like a game - it's a true to life sim. To me, knowing that I am even on the same playing field with those famous racers makes the fees worth it.
People often complain about how the rookie cars "slide" through the corners - but that's just the thing, it's only the rookie cars. You won't be doing that in the Star Mazda or the SK Modified (or anything else for that matter)...You have to actually "prove" you are able to control a car before you have your license upgraded.
Alot of people also complain about all the wrecking in the rookie classes...that's because it's the rookie class - don't race there if you have the ability to race something else. If not - race, race and race until you can get out of it - there's a TON of clean racing to be had, you just have to get out of the rookie races to find it...however, I still find it fun to race the rookie legends - what a blast! Besides, if my rating goes down because of a wreck, it's easy to make up in the next race!
As for comparing it to LFS - it's apples and oranges. I love both sims (even though it appears that LFS development has come to a painful halt - which is one of the few faults I can find with LFS). In LFS I mainly race the MRT and UFR now because they are quick agile little things, and it seems like I get a better sense of speed when compared to other vehicles.
So while I do enjoy iRacing, I will still run LFS, alot.