Mad Moxxi DLC is out for Xbox.
I'm playing right now, and it's pretty cool so far. It's got a lot of style. The music is this bass heavy techno that I actually like (I don't like much techno), and Moxxi sits there and yells about who's doing good or whatever. I'm playing Lilith, so she's talking about Lilith beating up on all these big mean men and such. I started on playthrough 1, even though my character is 42. The initial quest (to survive 5 rounds in 3 different arenas) was level 15, but then when the enemies came out they were level 42. 5 rounds make a wave, then you get a piece or two of loot (loot was level 37 adn 40 for me), and the next wave starts.
Moxxi throws in some random effects to keep things interesting. Some of the stuff I've gotten in just 7 rounds (1 full wave of 5 rounds, and 2 rounds from wave 2):
-increased pistol dmg, lowered dmg to everything else
-zero shields, but added some low health regen, and with lots of the guys that run at you and explode
-huge boost in damage, but huge hit to accuracy