though i will concede that for many people, Linux isn't the right decision for the desktop (some things are more difficult to do, and integration with running windows apps isn't perfect yet)...i think that for servers, Linux and other UNIXes win hands down.
let's not forget OS X is a BSD operating system, a derivative of UNIX. and there's MANY people using that now. Heck, even Microsoft uses BSD for their stuff..what do you think hotmail runs? :)