Well, I have not followed this discussion, so ignore this if you have already covered these kinds of things / this is not something you are looking for.

About a year or two ago I changed from C++ to D in my freetime projects (like simulator in my Thesis about cellular computers). When I was programming a sudoku puzzle generator, I wanted to explore analytic sudoku solving (to understand, how to generate easy/difficult puzzles) and I needed a GUI to be able to follow the solution. So I get my old "application browser" concept from naftaline, translated it to Java/Swing and named it JAB - of course, it could be translated to e.g. D with Xlib, or any other language and widget set.

    http://reaaliaika.net/showarea.php/appbrowser

Certainly, it's far from being ready for public, but that's the way I got GUI to my D programs...