They could have done so much more...
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I would like to [continue] my review by correcting something. When you die while fighting in the Underdome you have to restart at the first Wave of the PREVIOUS round, NOT all the way back to the beginning. So, for example, if you die at some point while in Round 3, you will restart at Wave 1 of Round 2. This extremely sucks if you die late in Round 2, basically making you restart completely (I have only played this in single-player, so this may be different in multi). This really isn't that big of an issue for anyone that is used to playing Survival Mode in a game. I used to play Nazi Zombies for an hour or so before dying, and then I would just restart and do it all over again.
Anyways, I have mixed feelings for this DLC. For months I was hoping for a Survival Mode to come out for Borderlands, which is sort of what the Underdome is, but they could have done so much more with it. The noise of the crowd is awesome, and Moxxi's comments are quite funny. The horde wave is definitely a rush. The fact that Skags (EDIT: "and Guardians") are the only "creature" enemies in the DLC is just a huge dissapointment. With all of the creatures Pandora has to offer, they really dropped the ball on that one. I was hoping to face an onslaught of Spiderants, but I'll just have to do that outside of the Underdome. I wish all of the enemies on Pandora were in the mix.
Upon completion of the quests required from Moxxi, the player should be able to configure the Arena's as they please, with lots of options available. The possiblities could have been crazy. Yes, it would still get repetitive, but Gearbox had the perfect oppurtunity to offer an awesome Survival Mode with tons of possibilities. I hope they offer something like this in the future.
I gotta say though that it was worth $10 for me. I've already played in the Underdome for about 6 hours, and I'm still enjoying it. Cheers.