I'm in an office with a very tight IT budget so I try to push open source wherever possible. For basic image editing, I've turned some people onto Gimp. One frustrating aspect of Gimp—because it runs under X11 and is not a native Cocoa application—is that ever time you want to choose a tool from the toolbox, you have to click the toolbox to select it, and then click again to select the tool. It's frustrating when all I want to do is make a simple edit. I've just located this solution:
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090817083346589