A lot of progress has been made toward porting the GTK+ library to OS X, and recently intructions went up on how to build Gimp for native OS X operation. That’s right, without X11 getting in your way. It’s still not ready for prime time, but I’m really excited about where it’s going. If you’re a programmer and have some brain cycles to spare, this might be a fun project to contribute to.
Gimp Running Natively in OS X