I use Qt.
I'm not a programmer, just a hobbyist in programming, and my opinion is as the following:
I think it's great. Kubuntu uses it, KDE uses it, Telegram also uses it.
I like the ability to drag and drop buttons like in Visual Basic to produce a GUI rapidly using Qt Creator and/or Qt Designer.
I like how complete the examples made available built-in Qt Creator.
I like the integration.