I just got GT4, all I can say is WOOOOOOOOTTTTT!!!!!! This is the game the earlier versions SHOULD have been! Real-ish cars on real tracks! The game has an option to force hi-def out of the standard-def PS2, but it's 1080i only (no 720p) and the setting cannot be saved, you have to set it every power-up. 16:9 pic, Dolby Pro Logic, no DD.
Unfortunately, I have heard of a lot of PS2 systems crapping out. This one acted a little wierd with Madden 04, but it didn't go belly-up. Fingers crossed.
Consoles vs. puters- Each has it's place. If it's one or the other, puter every time. I regret spending the dough on the PS2, just to play Madden and GT.