I know I'm going to get a "if you have nothing positive to contribute, don't say anything" comment, but here goes.
I can deal without Ferrari and such. Online is cool, but I don't NEED it. Get off my ass about damage. "Whoa! That car hit the wall at 155 mph and showed no damage. AWESOME!" But if I had to choose one, it would have to be the wait. But remember this. Half-Life 2 was recently released, and that game was supposed to be out last year, I believe. And now look at it. PC Gamer gave it 98% (I think 85% or higher gets a "PC Gamer Editor's Choice Award" or something), G4TechTV show "X-Play gave it "5 out of 5," and it's pretty much a hit. And even this waiting and delaying doesn't make the game any bad. If HL2 acheieved high ratings without delay, I'm pretty sure GT4 can acheive the same results.
Only because I have to choose SOMETHING from this poll, count me in on the wait.