Dirk talked at Linux.Conf.Au about the adventures over the past year in porting Subsurface to Qt. Subsurface is the open-source application developed by Linus Torvalds, himself, and other developers for being a divelog program for archiving their scuba diving adventures around the world. While Dirk and Linus aren't enthusiastic front-end / application developers, they have found Qt to do much better than GTK for their cross-platform program.
During the LCA 2014 talk, Dirk Hohndel shared what he viewed as the biggest problem with the GTK tool-kit... It's not the lack of great cross-platform suprport or some technical item, but, "the biggest problem with GTK is the attitude of the core community."
Dirk shared the same view as many with dealing with upstream GTK/GNOME developers being tough, frequent abuse and flame-wars, and accusations from the developers that "you're doing it wrong." Dirk found that the Qt development community was quite the opposite: Qt developers were willing to engage and help, there's plenty of application developer documentation, and there weren't communication problems like found when dealing with GTK developers.
Porting Subsurface from GTK to Qt took about six months. Other praise that Dirk had for the Qt tool-kit included the qmake build system, the native widgets for OS X / Linux / Windows, and other highlights. Dirk also found the Qt Creator IDE to be incredibly good. Dirk even switched from being a long-time emacs user to now using the Qt Creator integrated development environment.
For those curious about more of Dirk's thoughts on GTK vs. Qt and their porting adventures, the LCA 2014 talk can be found here (MP4 file).