It's a fun game, people should give it a try. It handles quite differently from a typical TPS: it doesn't have a cover stick system, but covering is important and so is staying discreet in confined spaces, all guns handle differently - short bursts are recommended (but not for an automatic shotgun) and driving is about as good as a GTA-clone gets. Because it is a GTA-clone from one perspective, it is still a MMO, so it is not from another.
What got me hooked at first is its great urban style with lots of customization options: no two characters will look the same. What I will stay in it for is its fast-paced gameplay: you press U to join a team, K to get ready and bam - a second later you're racing to an objective in hopes of being able to complete it. Also it gets very tactical very fast and teamwork is a key to success. In this regard APB is actually a lot like CS, only from a third-person.
All in all, there is absolutely no reason not to try it out since it is free (well I can think of one: you need a pretty strong system to be able to run it, graphically it's a lot better than GTA4). Definitely a better free MMO out there.