Shortly i worked with gimp some pictures for a webpage and i noticed that 
the open and savedialog isn't very comfortable; for example when your 
images are in e.g. /mnt/ mounted from some other machine and you want to 
save the processed images in /home/jakob/work then you'll always have to 
click yourself throug all the directories and that's very ineffective. 
 
So my recommendation would be at least some 'Forward' and 'Backward' 
buttons like in konqueror; also a button which teleports one back into  
his home-directory would be great. Further some kind of location bar 
similar to the save/open-dialog of konqueror or win2k which can be freely 
defined would enhance the usabilty of the gimp. (o: 
 
Jakob