I've been through this myself. I've used Qt in the past for work but for my own purposes it's too heavy and intrusive.
The first alternative I used for a couple of years was wxWidgets. It's actually pretty nice and has a lighter-weight framework than Qt.
I recently switched from wxWidgets to fltk. fltk is very lightweight but you have to do more work yourself.
Philosophically I don't like GUI frameworks like Qt. The main problem with Qt is your whole application is Qt-flavored from top to bottom. The reason for this is Qt and similar frameworks define all their own types, from Qstring to Qthread. I wanted to use C++ native types whenever possible. Also, Qt and similar drive the design where your code runs within Qt. Again, philosophically what I wanted was a lightweight GUI library that *my* code would call, not the other way around.