I just put a bow on Zeta and I must say that although I really enjoyed the first third, the back two thirds were downright boring. It was definitely interesting to face aliens for the first time but once I got a disintegrater the combat just became downright boring. The three generators seemed like a way to artificially lengthen it, and after about an hour I just wanted it to be over with. I did manage to pick up some useful guns, and plenty of ammo of one of the guys I killed, so it wasn't a complete waste but I now understand why people think this is the weakest of the DLC for Fallout 3