Don't let horror stories of over exaggerated horrible installation and performance issues.
Anyway, For me, installation was easy, albeit slightly long but I had no problems, performance is all right for me, nothing great, I have a 9800GT with a Q8300 Quad core, I usually get 40+ fps with shadows off, Textures on medium (can go to high but stutters due to resource allowance thing) and everything else on very high, the game still looks great.
A little about the game; The Player, Niko Bellic is fresh off the boat from Europe, ready to start a new life in America, with his cousin; Roman, Niko is your typical Eastern European badass with a nose only to match the size of his badassery.
Anyway, the physics are among the best I have seen in any game, or at least by far the most realistic, the sound, and look of someone's bones breaking against your car grill is the most satisfying thing, to satisfying to describe. The rest of the mechanics are fairly solid, the gun play is pretty good, although tedious at times with the slightly clunky cover system, driving is realistic, and anyone who complains about it being "bad" I'd tell them to hop in a sports and try to handbrake turn at 200mph and try not to spin out of control.
The characters, and story are as interesting, if not more so than the previous games in the series, the story is fleshed out and is overall generally interesting.
There are parts however where it makes me think, the turn to "gritty realism" was not the best choice, taking your friends bowling or eating can be boring, and the "realistic" movements can make for clunky controls, I often found myself bumping into an object, to turn around and bump into the other side, or something else. And once you look past the pretty visuals and physics, you'll notice there is a lot missing that was there in previous GTA games, such as the customisation, however, at least the graphics and physics do a good job of keeping that covered up until the end game.
Overall, I think a 9/10 is appropriate, performance is nothing special, but fully patched and you'll find most issues people were complaining about are going, the reason I am not giving this a 10, is because it is still missing something, the core GTA gameplay is there, but it has nothing unique, other than the physics that really set itself apart from the rest of the series, however, it is still a great game, and I recommend it to anyone, for any platform.