A lot of questions arise about the Avalon Reef Club on Isla Mujeres. I thought I'd post this link that summarizes my experience from December of 2002. Purely my impressions and my photos... feel free to follow up with any questions.
Basically, the Avalon Reef Club is in a gorgeous location. If you can get a good price for the room, and don't mind traveling into town (about a $2 cab ride or 15 minute walk) to sample the awesome restaurants on isla, it's a nice place to stay. As with any hotel, it depends a lot on what's important to you as well. I liked the private balcony on my villa studio room, the quiet environment, and the clean, comfortable room. I didn't like the sense that no one in particular cared that I was there.