This is from my review of the whole game...
Now one of the most disappointing pieces of downloadable content is Mad Moxxi’s Underdome. It is basically a string of arena style combat tournaments which throws wave after wave of enemy units at you that are brutal to tackle by yourself as such I suggest play as a team. This basically continues the trope of horde mode from Gears of War that has been circulating in the FPS genre. I have not been able to get through the tournaments because of the individual difficulty but from that I find it frustrating that they put this up as a ten dollar add-on. The only good idea to come out of this is the weapons bank where you can store some of your unused but horde worthy weapons. This was a disappointing use of ten dollars.