I installed Ubuntu on an old Dell GX150 several months ago, and I must say I am impressed. This is my first real foray into the Linux world, and while I can run rings around most windows users in the command prompt, I have been a little nervous about starting Linux. Of course some Linux users will probably say I haven't really started using Linux yet. And since the install and configuration of Ubuntu is all easy and gui driven , I would agree that I have not really gotten into the guts of the OS like I have in Windows.
But I am slowly learning about Linux, and soon I hope to install Xubuntu on one of these GX150's I have, so that I can compare the two distros.
And after that it's FreeBSD, or maybe Haiku. I could run a vmware session of Haiku I guess. Or maybe I will just pick a random OS from the FreeOs website.