I honestly can't imagine how working with the UCMP could be any better than it is, unless we all shared an office and got paid for it.
The team values constructive criticism highly and none of us are afraid to tell the others what we think. This, combined with a thirst for learning all we can about each aspect of level design, is probably the two aspects of being a UCMP teammember I value the most.

UCMP Website

.....I joined the UCMP when it formed, back in November, 2004. At the time, I had a map, DM-Xanadu, that was, I thought, almost done. Working with the UCMP, I ended up making custom textures and meshes for it and solving some very bad opimization problems.
.....I also got to work closely with a few of the mappers, JuggaloKyle and Stormblade, to produce DM-UCMP-PleasantValley. Collaborating both with them and the other teammembers, has been the best thing I've done since I started mapping.
.....For UCMP1 I also got to work closely with founder MichaelM and I ended up designing the UCMP1 website, and managing the UCMP1 promotional video project which involved 4 other members.
.....DM-UCMP-Xanadu was released with UCMP vol. 1 and the map would not be half as good as it is without my experience with the UCMP team.
.....Because of a new commitment I made to another project, I pulled my proposed maps for UCMP2 and focused on backing up the team. In August, about 2/3 of the way through UCMP2 development, MichaelM had almost dissappeared from the UCMP due to being eaten alive by Real Life. The other UCMP members were kind enough to 'elect' me as thier new leader, and, with the help of the team, I steered the UCMP2 through an accelerated development phase to release. I also redesigned the UCMP website, and with the help of 2 other members, completed the second UCMP promotional video.
.....Now, I continue to head the UCMP team. We have become more organized, focused and have set up a 'framework' in which to develop. Despite the hard work involved, the team makes it easy, and I continue to learn from them, and enjoy my time with them every day.