One think that GTK will allow easy implementation of is OpenGL alpha
transparency in
the drawing. For those without accelerated graphics you'll hate it, but it
will be a great
improvement for those with fast hardware.
The future is now, and an opengl card is cheap (even in my country).
For PCs, anyway. Please keep in mind that some of us don't use PCs.
I really have no words when I see the 3d rendering of a board in the Kicad, and sometimes that is really usefull. gEDA and PCB are professional tools and I really dont think that a pre-requisite to them is to run on old machines. MHO, of course.
Where "old machines" means "anything that's not a PC"? I think not.
-Dave