During last days, I have being working with one program which uses GTK+ 2.22 for its user interface. It works, but some things look as something foreign on Windows XP. In particular, this is strange folder opening dialog, lack of flashing of active modal window title when clicking with mouse on inactive parent window, and some other small things.
My conclusion is trivial: if you target only one platform, it is better to use GUI libraries created for this particular platform that fully complains with established de-facto standards.
