Borderlands brings us the best co-op and split screen experience since....EVER!
In-fact, I would rather you go out and buy this game right now than spend the time reading this review, but there is one thing that you must consider...
The game has a poor drop system. Any player can pick up any weapon at any time. This means that you are going to be ninja looted unless you ninja loot back. It creates a vicious cycle and its hard to work together with people who just stole the perfect epic gun for your class along with all the other items you could use.
So you might loose your epic gun from time to time to another player, but its still worth buying this game. Those green and blue guns work fine anyway =).