Ive run Ubuntu, Fedora, RedHat, Mint, and Mandriva. My favorite was Fedora, but it doesnt have quite the support that Ubuntu did. The programs I wanted were hard to find in a .rpm format from the repositories. I tested most of these in a VMWare Workstation. I also dual booted for a few months with Ubuntu. I found myself never booting into Ubuntu even though I set it as the default OS in the Grub Bootloader.
Linux distro's are better for some things, but for 99% of the stuff I do with my job and for practical purposes Windows is the way to go.