A Lot Of Fun While It Lasts - Just Make Sure You've Got A PC That Can Handle It
As you'd expect the physics in the game are impressive and even without the ageia ppu enabled the game offers quite a bit of fun - though when you get into the areas of the levels which have fluid systems even my mighty quad core showed a bit of slow-down without the ppu enabled. Graphically, it's got a pretty decent checklist of best-of-breed DX9 effects like HDR, Per-Pixel Motion Blur (which will suck up the cycles like crazy) and decent smoke effects.
The level design is uneven - often times really good and other times just ok - but there is never a point in which it's terrible.
You'll probably have the most fun with the bishop character, smply because the freedom that her psi powers provide you give you almost a limitless number of ways to kill your enemies. You can get a huge ball of boxes, for example and use it to both defend yourself from rocket attacks and smash the enemy, and it feels incredibly satisfying doing so. Other fun points of note include the lava streams which can be manipulated by the balck ops and the bishop character to form weapons.
I'd also recommend spending some time watching the included tutorials which provide a good jumping off point.
the bottom line is that if you've got a decent system - the kind that you might be prepping for crysis or quake wars - the gmae should run smoothly for you and you'll have a lot of fun with it.. you can't beat the price and if you've got an ageia ppu in your machine, this is most certainly the best use for it yet.