I've been using Linux OS's for about 7 years, always on a dual boot system because find there are some things I just have to have Windows for.
OS experience in no particular order:
Slackware 8 - 10.2 (soon to install Slackware 12)
Various Red Hat and Mandriva versions.
Ubuntu and it's ilk.
Gentoo stage 1
Damn Small Linux
Though I have to say, if you want to learn how to use Linux, get Slackware or Gentoo. Those puppies will teach you a thing or two.