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It's pretty much Mad Max meets Diablo. They have this system where guns are randomly generated and in addition to the usual differences among firearms (sniper rifles are long range, shotguns work best when in close range), they have individual stats in the form of stocks, sights, barrels, bodies, and cylinders (or chamber).
Basically, if you like having the biggest, most badass weapon in whatever game you play, this should keep you occupied finding the biggest fuckin' shotgun EVAR.
Another area Borderlands is using is classes. Rather than in shooters your class affects your weapon and equipment loadout, in this game you get special abilities. Each character has a specified role, such as spellcaster (the pale alien chick), sniper, tank (the big guy with fists), and the soldier class can heal.
Coupled with four player online co-op, this looks to be what I will be spending the bulk of my time and money on when it releases.

Also, here's my ID of the now
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