I played through Borderlands as berserker. I played some with a friend, and that was amusing for a while, but my internet here is crap for online games so I went mostly solo. I have to say, by the time I made it to the caverns or whatever where the vault was in, I was just using my berserk in order to sprint through everything instead of actually kill anybody because it had become so monotonous and tedious it wasn't fun anymore. I just wanted to see the end of the game. It probably didn't help that the game was really easy. Even the big fights against the big monsters, like skagzilla, was super easy, it just took a long time to kill him.
Honestly, I'm sure I would have had more fun playing with friends, but as is if you don't know anyone who wants or owns this game, don't touch it, unless you like a boring shooter with no story. The only thing that I really liked was listening to that one woman's journals of her expedition. They were amusing.