Personally I had a lot of joy out of Gimp on the N900 for small things.
I used it a lot for modding .png's when I had Androud devices. I made new icons and modded lock sliders for widget locker. Very convinient for small jobs and easy to transfer through BT.
Even found it was easier to install fonts and make some plugins work on the N900 that I just couldn't get to work on my laptop.
Also made costum splash screens for android devices on the N900.
To me Gimp on the N900 was pretty cool to have because it was a desktop grade app that no mobile app could nor can match still for the above mentioned things.

Dousan...