Only for developers that aren't savvy enough to know the multiple options to bundle the runtime or compile to native code.
Or the users that don't install Java from http://www.oracle.com/technetwork/java/javase/downloads/jre8... or can't be bothered to read a dialog box.
> or that seem borderline-unsupported (X11/Quartz)
Since when is Quartz unsupported?
> or that require funny multi-stage compiling (Qt).
Since when do users compile GUI frameworks?
Cross platform UI is nothing new, there are much more options to choose from than those you listed, and browsers can hardly offer more than a 90's GUI experience.
