I played a couple of them about 2 years ago. I was never in it for the multiplayer gameplay, though. I just liked well-crafted levels with good writing in the descriptions, along with unique and thought-provoking quests/puzzles. I went through this whole text-based games phase where I got down on Collosal Cavern, Hitchhiker's Guide to the Galaxy, and any decent MUDs I could get my hands on. They're really some of the most challenging games you can play (took me so long to avoid that stray flying brick at the beginning of HGttG).