I too am a big Mindcrack fan. We actually did UHC on April 1st, 2012 with the goal of killing the enderdragon. We had to cut the process of finding the stronghold due to time constraints (dead people wanted to play), but we got potions and defeated him. It was fun, but a very long day. (~7 hours)
The problem with competitive UHC is it’s really easy to cheat. It works so well with the Mindcrack guys because they all record their play sessions. That’s partly why we did the enderdragon fight instead (which is what UHC Season 1 was). I’ve tried coming up with ways of making this work, but it’s difficult enough getting everyone to play a short 10 minute game (and fairly), let alone a game that lasts a few hours. My favorite idea is to use compasses that point to one random competitor.