>>7
UI designer = programmer and in the case of GIMP, also graphics designer who wants to use GIMP for real work, unless you want the project to fail.
>>9
GIMP needs an MDI interface. It looks better and doesn't mess with other applications, but the main point is to dock all toolbars and its stupid free windows somewhere, so they won't be hiding/getting hidden by your images ALL THE FUCKING TIME, especially when you zoom in/out which you usually need to do a lot.
I, for one, like GIMP's UI.
You've said it, "for one". May I ask if you did any real work with it? Real is at least 5 layers and at least 5 MPix, or a complex skin or web interface consisting of 20 or more image files, preferrably vectorized OH WAI-.