Qt is amazing. That's why all the best Linux apps (Dolphin, Okular, KolourPaint, Gwenview) are Qt apps while the GTK competitors are toy apps by comparison. And probably why GNOME's philosophical cornerstone is removing features with every update.
Yup couldn't agree more. Qt is the most productive and one of the nicest GUI framework I have used during my programming career. Used it from C++ and also from Python (PyQt). And on top of it it is also the best I have used when it comes to very good native OS integration (looks, behaviour...) when you need cross-platform support. GTK+ yeah not nice, I am trying to forget it just as all those Java GUI frameworks. Terrible experience.
Is there a Qt app that looks great on Windows? Breeze is awesome when on KDE, but I don't remember a single Qt app that'd actively look good on Windows.
Yeah I'm not sure if it's Qt but the whole design philosophy of "user choice matters" really makes such a difference between software you can rely on and stuff that's just in the way like gnome or macOS.
