"This is part of the reason I don't think cross-platform apps with different skins are really practical. Users expect certain behavior that is implemented by the native widget set. Linux behavior with a Mac OS X paint coat does not make a Mac OS X app." Bob Ippolito said much the same thing in his PyCon2004 talk about using the PyObjC bridge to develop on Mac OS X instead of wx-windows, TkInter, and the rest of the cross-platform GUI toolkits.