Brilliant!!!
The graphics and overall look of the game is very impressive. Liberty City actually looks like a real city with real people living there. However, in some of the cut scenes the graphics don't look quite so great but thats a minor point really. The story itself is very engaging I quickly progressed through it at first until some of later more difficult missions which a couple of attempts. I also liked the parts of the story where you can make decisions yourself and they have actual consequences in terms of the story later. This is the first GTA where I actually liked the character I was playing so I guess I enjoyed the game more.
The multiplayer element of game is great and adds longevity to the game. I haven't tried the racing mode because my driving is pathetic (I usually have to change cars about 3 times when driving across the city) but all the other modes are very enjoyable although the controls do feels sluggish.
Overall I would say that GTA4 is a brilliant game that certainly lived up to the hype.