Few people know that in recent versions of QtCreator there is support for QML Live Preview - the ability to edit the code and immediately see the changes on an already running program, both on the desktop / emulator and on the real device. A wildly handy thing, saves a ton of time in the UI development / editing phase.
All this, along with other debugging QML plugs, works out of the box on QtCreator versions> 2.3. For Qt version 4.8, QML debugging is enabled by default, for 4.7 light gestures are required in the form of pressing one button .
A small demonstration of how this works on the example of the Nokia N950: