If the latest gameplay trailer for Realtime Worlds' APB doesn't have you drawing comparisons to Grand Theft Auto, then you probably haven't played Grand Theft Auto.
McWhertor mentioned the similarities between the two titles in his impressions of APB from Gamescom in Germany last month, and this gameplay clip completely backs him up. Of course this isn't a bad thing. I've had countless hours of fun just tooling around in Free Ride mode in Grand Theft Auto IV, so I could definitely see the finer points of a game that takes that and gives it a direction.
In short, I'd totally hit it, but I'd be thinking of something else.