maybe you read already, but is an interesting post about

http://thpmaemo.blogspot.it/2013/07/...n-on-qt-5.html

"Lightweight can be achieved by not binding all the Qt classes, but only the ones you really need for creating QML applications. And responsive can be achieved by making sure that the interface between QML and Python is asynchronous, so the UI never blocks even if Python is working hard in the background to fulfill the requests of the user interface."