Long time users of Photoshop, the image editing program (so to speak) may have a problem getting used to Gimp.
The first problem is the that it takes some time to get around the question, “Why the heck is software that is so much better than Photoshop in some respects, available totally free?”. I leave you to work your way around that problem.
What I can help you with is the other problem – relearning how to accomplish different actions in Gimp. The gimp project has called the GUI the Graphical User Irritation or something in the past, if I recall correctly. Back in the days when I was a novice Linux user (not that I am any better off now, really), I found it interesting that the whole Gimp menu appeared when I right-clicked on the image. I thought that was neat, but it had it’s problems and all that. Now Gimp has windows-style menus and all that jazz, but some of the features or tools in Gimp have names that are different from Photoshop, and the menu is differently organized.
Now, with Scott’s GimpShop, Gimp behaves like Photoshop(Go ahead, check out the screenshots if you don’t beleive me). There is a Linux port of GimpShop too, if you need one.
So save the $649 for something better. Use Gimp.
(If you were a smart ass like me, you’d be using Ubuntu as your OS already 
, and saving and feeling good about being smart. )
Note: The author of the above article acknowledges that rising at 4 A.M. to work, and then taking a break after just 3 hours is not too smart.