I consider Borderlands to be Diablo II with guns. Played through as the Soldier with a Siren and Hunter. The turret beefed up all the way does solid damage when you run up on groups. And being able to shoot your teammates to heal them is PRICELESS. 2 thumps with Sledge's shotgun and their health is full again. I would drop my turret and sit back and keep shooting the siren to keep her up while she charges in for a melee run.
Fun, but I had just come off of playing Fallout 3... so Borderlands seemed pretty shallow in comparison. I want co-op for Fallout: New Vegas. Or hell even STALKER.