In my opinion; if you're experienced with C++, try wxWindows, it's a whole cross-platform GUI Toolkit, it is easy, and completely logical.
I'm experinced with Python and Tkinter, but in my opinion wxPython (wxPython is just a python module that wraps around the wxWindows C++ library) is great. It's pretty easy to learn
(Even though there are only a few tutorials available (Well for wxPython.. I heard the wxWindows documentation is wide.) It's easy to catch on with.)