Except for the problem of out of date software... :)
server and desktop have different stability requirements. on a desktop i just need all user apps to work well. on a server i need things to be rock solid.
the newer the less stable things get. the distros i am familiar with i would sort in this order:
RHEL/centos > debian/ubuntu LTS > fedora/ubuntu > debian testing
fedora and ubuntu are stable enough for a desktop or client, but i'd never put them on a server.
The package manager/distro model that Linux employs only ever seems to give you the choice of one or the other, because it doesn't have a clear differentiation between "OS" and "application".