I've played for about an hour now, I guess. I only played it once on PS2, so I can't really compare to that. I just installed WinXP last night, and I haven't beaten my gamepad into working just yet (Windows recognizes it and says the D-pad works, but GTA doesn't yet, for some reason - not sure why), so I was playing with the mouse and keyboard. It works all right. The mouse is really used only when you're on foot.
The graphics looks pretty sharp and the sound is also good. As can be expected, you can put your own MP3s into the game and listen to those rather than the somewhat cheesy music that comes with the game. One of my friends who also bought the game says that you don't have to put the actual MP3s in the music directory, just shortcuts, which was a good idea for Rockstar to do.
As far as gameplay, it's basically everything I was expecting and hoping it would be. Like I said, I can't compare to the PS2 version, but if you've played that, I'm sure that this is very similar, perhaps graphically enhanced. With the little time I've played so far, I can definitely say that I recommend the game.