I've tried a few distros over the years. I wasn't particularly impressed with Red Hat (7?), Fedora (Core 2?), or Debian (Woody?). It wasn't until I tried Mandrake 10.0 that I found something I could make my primary OS.
Of course, the whole Linux software ecosystem has improved during this time. I'm sure the latest versions of those other distros (well, if I were to use Debian unstable) are very liveable nowadays.
Also, the fact that Mandrake uses KDE as its primary desktop made the transition from Windows much easier.
Nowadays, I'm using and recommend Kubuntu. It is so great to have a CD you can boot up from, try out the OS, and then install from -- man, does that beat the bad old days! I've also tried Ubuntu and Xubuntu, and, with luck, with have thin clients working with Edubuntu today.