I've written a few GUIs in Perl/Tk for a small group of windows users, and haven't received any complaints about the interfaces looking funny. The only difference between the way a Tk app looks and the way some of the standard apps in microsoft office look (at least the only difference that is obvious to me) is that the Tk apps stick a little "Tk" in the top-left corner of the apps' main windows.

Is there some specific limitation to Perl/Tk interfaces that you're concerned about?