Always wanting to break free from Microsoft and run Linux, Adobe Photoshop is the only application that keeps me using MS-Windows. I heard that GIMP is a good replacement, but I'd like some first hand experience from the real world. Anybody tried or used it?

http://www.gimp.org/
"GIMP is the GNU Image Manipulation Program. It is a multiplatform freely distributed piece of software for such tasks as photo retouching, image composition and image authoring. A free replacement for Adobe? Photoshop, with loads of plugins."