wxPython and pyQt / pyside are probably the easiest to use on all platforms and will look right on most Operating systems. I know wxPython is specifically designed to wrap the native widgets so if you want your app to look native, I think wxPython is the way to go. If you want to be able to theme/skin your app, then PyQT or pyGTK may be better. PyQt/PySide supports mobile
wxPython and pyQt / pyside are probably the easiest to use on all platforms and will look right on most Operating systems. I know wxPython is specifically designed to wrap the native widgets so if you want your app to look native, I think wxPython is the way to go. If you want to be able to theme/skin your app, then PyQT or pyGTK may be better.
PyQt/PySide supports mobile