I've been using the Gimp (the GNU Image Manipulation Program) since before the 1.0 release. I started messing around with Linux around the same 96/97 time frame. Yay RedHat 3! I think my first distro was actually a Slackware install... I just remember it being a pain. I do remember the long ass time it took to compile the code to run gimp, on my awesome 486dx4 100mhz beast with 8mb of RAM... Wooo!
I must say it has improved drastically since those days. I do prefer Adobe products over the Gimp in regards to functionality, however, there aren't a lot of standard things you can do in Photoshop, that you can't do in the Gimp, if any...