I still wish we would've done more with Xt instead of reinventing the wheel again and again. So when gtk was founded, they could've just replaced the Motif part of the GIMP, not start anew. I'm actually surprised that they didn't invent a new language back then. Well, there's Vala now, after that brief dalliance with C#.
http://bitway.com/jordan/papers/USENIX/AppDev.html was a pretty interesting paper way back when.