I don't know why so many people moan about the game saying it's a failure.
It runs great on a gaming PC, granted your doomed without a quadcore, but they're becoming more and more common these days.
The game also has incredible mods, awesome online multiplayer, and it's not buggy at all - there are a few minor graphical glitches. But it's just excellent overall. It has the bonus of a great video editor too.
I would strongly argue playing with your best mate in a private GTA4 freeroam game is more fun than any other MP game.