I ended up using Ubuntu 8.04 64-bit as my work desktop for possibly 10 months. I chose this after failing to get newer OpenSolaris release to boot on my quad-Xeon CPU (latest 104 Solaris kernel still does not boot).
Ubuntu is excellent, I'm quite used to Debian and Ubuntu at home, so setting them up at work was easy. Showing off apt-get to people really impressed them. I did have issues with being stuck on openoffice v2, but I could cope with that. I did want to try out the KVM virtualisation technology, but that was quite lacking in Ubuntu; it never started up properly or worked.
I wanted to switch to a distribution that was more KVM friendly so I decided to wipe Ubuntu and go with CentOS 5.3. But waiting for 5.3 took too long for me, so I went with Fedora 10 64-bit :-).
I've used all the distros at some time, so Fedora was not new to me. It is an excellent distro.
I had only a couple of issues with it :
1) nvidia driver problems - resolved by adding another repository source
2) constant yum issues - the PackageKit would hang and lockup all the time
3) yum is nowhere near as good as apt
But I've been very happy with Fedora 64-bit. It has everything I need in a corporate development environment. The other developers using Windows are constantly surprised at Fedora features.
Since then, I have upgraded to Fedora 11, which is even better. But I would not recommend the upgrade, you should format and install the new Fedora 11 fresh. I've had lots of issues with clashing packages and dependency problems, but I have resolved them all. PackageKit now works.
and I've been experimenting with KVM vs. VirtualBox 3.0.2.
