i work with HPUX, Solaris, AIX and RedHat Linux. Fedora being an offshoot of redhat, enjoys the militant standards adherence of RedHat, and has been a much easier learning curve than any other *nix i work with.

i havent played much with the other linux distros out there, but i would guess the ones that stick to standards are going to be easier to learn. i started working with windows, and have moved into a more linux based user, and do enjoy the choices presented, challenges to learn new technologies and the cost benefit of open source.