I like using GIMP because it's what I use on Ubuntu and Suse and I use a lot of different machines (two XP boxes on different networks at work, several OSes at home, and I change jobs every couple of years). Photoshop isn't cross-platform, and the licensing would be prohibitive for my needs. For my brother, a professional artist with his own studio, Photoshop is the only way to go. For my daughter on a Cr-48, GIMP is great.