What's interesting about this game is the clash between great ideas and terrible ones. On one end, you've got the fantastic team mechanics, great weapon customization, fun levels and original set pieces, but on the other end, you've got a bad interface, a strange control scheme, a bland colour palette and, worst of all, horribly placed checkpoints before unskippable cutscenes. These bad aspects of the game never really ruin it (though the checkpoints come close), but they're really kind of a shame, as this could've been a far better game with just a bit more polish.
Still, this manages to remain very fun to play with a friend, and presents you with a rare thing: tough moral decisions. I found myself totally stumped more than once, not knowing which choice was morally sound. The final decision you make is probably the hardest and most ethically grey decision I've seen in a video game.
It's not worth buying, but a rental with a friend is highly recommended, so long as you prepare yourself for a bit of fiddling.
In a sentence:
Tons of fun with a friend and has some great moments, but hindered by poor design choices and a poor interface.