4 player RPG/FPS co-op! This game is a mixture of the best of Fallout 3, Army of Two w/ a touch of WoW thrown in.
There's no radio like Fallout 3 but it's not as linear as say MW2, the background music is quirky enough not to get stagnant, I almost want to buy a soundtrack to play while I'm driving w/ combat music playing during rush hour road rage.
There's a few glitches (the vehicle that I was driving got stuck a few times & Brick got stuck in a metal walkway once) but nothing that isn't too annoying that it can't be forgotten.
This game is a good distraction for me. I was playing Dragon Age: Origins & Fallout 3 and only came out to play w/ others for MW2 & ODST. Sometimes you just want something different and now there's Borderlands.
I played the 360 version, no idea if the PC version is worth it for me since I do most of my gaming nowadays on the Xbox.
Co-op mode means sharing cash earned. Picking up weapons is determined by which player picks up what & how much space in your backpack is available. Like the game says, share the loot so your group will be stronger. It isn't the greatest loot distribution system but it's something the company can work on for a sequel.
There's no other game like it on the market except maybe Army of Two but even that's only a 2 player co-op game. The leveling up is great, micromanaging character builds and multiplayer with your friends is priceless. The fact that your friends will probably like this game too is a bonus.