Well, I think Qt looks really pretty and generally prefer Qt apps over GTK versions. I find it nicer as a programmer too. I've known projects to migrate from GTK to Qt (in particular Rosegarden, which used to have a great blog post about how much nicer it made everything that I sadly can't find now) - looking at https://www.wikivs.com/wiki/GTK_vs_Qt there's a big list of projects that have switched from GTK to Qt and none that have gone in the other direction.