My friend brought it over, and I play some deal of it. I'm gonna borrow it and let him borrow BioShock.
I love the explosions and driving mechanics, the radio, the TV, the internet, the whores, the ability to throw things at hobos, kick people down stairs and the targeting/covering system. And I like that it's more realistic than San Andreas (i.e. there's no part where you go into an army base with nothing but an uzi and no shirt just to get a jet pac) but in my opinion it still feels a little too much like GTA for my liking.
Right now it seems like a great game, but in my opinion not as great as other current-generation games like Super Mario Galaxy and BioShock. S'pose I haven't played all of it yet, but that's my original impression.