I switched from Fedora to Ubuntu last week on my computer at work and I could not be happier.
Setup was simple. I really like the apt-get, gentoo portage and BSD ports model. RPM is just too much of a pain.
One interesting thing about Ubuntu is that there is not a standard root account. Just like you do with OS X, you have to sudo everything. That’s fine with me. And if you really, really need root, all you have to do is sudo bash and you are root.
This biggest annoyance is that I can not find a postgresql 8.0 package for ubuntu. I really don’t want to have to maintain all the startup scritps myself.
Otherwise, I’m very happy with it so far. Hopefully it will stay that way.