I just saw a talk and demonstration of Clutter - and was very impressed. Lots of stuff we are trying to do in Rapicorn already work well with Clutter. So we can probably learn from them. I wass impressed by the concepts of Actors (like label, rectangle), a Stage (as in screen), the way Timelines can be used to for instance move an Actor from one point on the screen to another while changing Opacity, Color and other properties according to a Function. Timelines are reversible (as in the widget moves in the center of the screen and back again), and the use of OpenGL shaders (which allows for instance blurring unused Actors). There are some nice demos, like Flutter for Fotos and a media player with cover support.