GIMP Interface Proposals?
Well I for one think The GIMP's UI is fine just how it is. Then again, I learned its UI when I was 13 or so, around the time I got addicted to sloppy/strict mouseover focus. Being able to point at a window and save its document by just striking Control-S is very efficient.
I thought GIMP was weird at first (I was a Photoshop 2.x user) but I rapidly came to appreciate its advantages. Basically, I love it because it's efficient and lightweight. If I want to do something to an image, I right-click the image. Simple, right? In Photoshop I have to hunt under some menu and I have to care about which image is in the foreground. And of course, in both, I can just use key accelerators -- in GIMP, even assign my own -- to speed things up.
You can't master GIMP in a day, and you sure as hell can't master Photoshop in a day either. Most of the complaining I hear is Photoshop users pissy about having to think a little differently to use GIMP. Maybe you should write a "tricks of the UI" tutorial for the unadventurous...?
Now if I were directing the GIMP project, I'd say:
Never adopt MDI. Well, okay, you can, just make it optional. There are a lot of Windows users who would love it, but a lot of current users who would dump GIMP in a second if it were mandatory.
Please rip off Photoshop's styles palette. It's one of the main reasons I use Photoshop primarily these days.
Please add serious ICC profile support wherever you can in the image workflow. Even if you don't support CMYK, good color support would rock, and it would make professionals take GIMP more seriously. Bonus points: add a calibrator like Adobe Gamma/Colorsync/Supercal.
Yeah... I think that's about all for now. Watch everyone disagree :)