It's not possible to GPL only for non-commercial development, so that's not really an issue. It's possible (by the copyright owner) to dual-license, and that's what Trolltech has been doing in the past. But the version that's GPL'ed will always be GPL'ed, and there are no limits to what kind of applications (commercial or not) can be developed.

In short, the restrictions you describe are not really there. I myself prefer to develop for GTK+, but that's just my personal preferences.