Interesting that Nokia picked it, given the TrollTech acquisition. Qt contains QGraphicsView, a Qt-integrated scene graph based system with similar capabilities for widget handling etc.
I'm not surprised to see it becoming popular in GNOME given it's pure-C implementation and APIs. It's odd to see it introduced to a platform that's moving toward Qt, though, especially one from a vendor like Nokia with a strong C++ (or butchered-pseudo-c++ at least) history. It might be a timing issue - and after all the Fremantle release of Maemo is a weird transitional hybrid in many ways.