It's fair to say that I like Mavic rims. But this is a choice made by nearly every serious rider. No matter who their sponsor is ... if you pull them away to talk privately they would but their life only on a Mavic rim.
For myself I use Open 4 CD road rims on my road bike. It is the best design.
I believe that the Mavic 231 is the best concieved design for a mountain bike rim because it uses multiple inner walls in a small shape making it intensely rigid. The 231 is slated to be discontinued in the fall of 1996, buy them now their sucessor didn't impress me as much.