Since I just got the sent in my 360 to Microsoft, I went over to a buddies house and got to take GTA IV for a test drive. The game is amazing I must admit, but there are a couple things I noticed that really effected my experience.
First of all, get used to cops because in GTA IV there is no escaping them. This was really annoying to me because I couldn't do anything without getting a cop on my tail and spending a good deal of time escaping from them. I would be on a mission, for example, and I would squeze by an intersection, accidentally hit one of many cop cars sitting there and then I would have to lose them. I am hoping however that Rockstar will release a 'no wanted level' cheat; that would be awesome.
Second, why is it sooo dark?!? I've seen this posted a few times already and please don't tell me, "It's the settings on your television because it's not. The brightness settings on my friends 32" HDTV were maxed out. I could not see a single thing especially at night time. I was on a mission for Little Jacob at night and it took my literally fifteen minutes to climb a flight of stairs in a darkened alleyway. I did use the 'brightness level' cheat and it made it a little bit better but still, waayyyy to dark.
Other than that the game is great. I loved the little taste of the storyline that I got, and I can't wait to get my 360 back so I can start my own game.