"What's the alternative to Qt in D?" should not be "Qt bindings" but maybe a library which imitates the implementation and/or interface of Qt UI widgets in native D.http://www.ohloh.net/p/qt/estimated_cost some scary numbers
http://www.ohloh.net/p/qt5dmd could really learn a thing or two from them: http://www.ohloh.net/p/qt5/factoids/15415862 ;)