Kind of late now, but there is more music in the game than the demo if that helps, I have the PS3 version though so I can't say if the PC version supports custom soundtracks.

I've heard less problems with the PS3 version than 360, but it seems no matter which one you pick you'll want to avoid PC. I personally went with PS3 and am loving the game.

The game is great, but other players are not. I try not to wreck anyone, but if I see someone that has wrecked me when they didn't have to, I make sure to pay them back. I don't get mad about it though, the game is made for fender benders.

I have it for PS3, and though some times I have to make 2 attempts to connect to RaceNet, the second time always works. There are a few glitches and lag in the online races, but that's rare, and the rest of game works fine for me. Usually have a full 8 other players as well depending on the time of day.

So, unfortunately it might be the PC version that is struggling.

I don't think you can get certain cars, but you do get more horns and paint jobs at least. I'm not max level though so I can't say how many.