I\'m looking to be able to build GUI applications quickly and painlessly as possible. I\'m competent (though not expert, and have no formal training) in C++, but have never used
I would suggest wxWidgets. To me, it's pretty intuitive and looks nice.
Code::Blocks was built with it, so check that out to see if you like the graphics.
There are also a slew of bindings for wxWidgets, such as wxPython, wxErlang, and others, so if you decide to switch off of C++, you can take wxWidgets with you.