Some nice little touches, but overall gameplay is shallow.
Some gripes about the gameplay are: poor vehicle physics, no real feel for firearms, and a non-immersive story/world.
Having said that it's not a bad game in any major way. It's just that it doesn't blow you away in any particular area and given the high standard of games out there it doesn't make a very strong case for your gaming time.
Some of the good points are: nice graphics, creative handheld weapons, good throwing mechanic, highly customizable player model (maybe too high), and a fairly quirky sense of humour.
In honesty though I played it only twice. I put in about 4-5 hours all up and didn't have the urge to go back. I sold it on ebay 3 weeks after I bought it. I'm sure there will be kids out there who'd enjoy it, but for the more mature gamer (I'm 27) you won't be missing out on anything if you pass this up.