Okay, phew. Been avoiding this thread to avoid spoilers for the past few days. Been playing for about 5 hours now, there's just so much to do in the world!
Haven't had any popping issues with the PSN version running on an SSD, but the framerate is pretty terrible most of the times. I'd say 30 FPS is the absolute maximum that you get if there's very little going on, but while driving in the city with busy traffic, you're going to go down to under 20 FPS and it gets really choppy, sometimes even very difficult to do missions as a result.
Physics... well they've gone more arcade and twitchy from GTA 4 as I expected from the videos. It's not totally uncontrollable, but the cars are too overly responsive and twitchy, far from the enjoyable and relaxed GTA 4 driving. Motorcycles are the worst offenders, they were nearly perfect in 4, but here they are mega twitchy and nervous, barely uncontrollable.
Those are the only negatives I can think of, I've loved everything else about it so far. The game is a vast masterpiece, that I feel like has been made for the next gen consoles in mind rather than the current ones. I'm almost certain that we're going to see a next gen console release once they come out, then the game would make much more sense with higher FPS and more enjoyable gameplay as a result. Not to mention, once it comes on PC, the twitchy handling can be fixed with mods.
In its current form with the outdated console performance, I'd give it a 7/10. Full HD and above with 60 FPS, 9/10.