The ability to get a constant stream of information indicating which areas of the view got changed and the rendered images of those areas.

Opens some new possibilities in JavaFX client programming like:
- recording animation that take place in a scene,
- streaming the scene to a thin client (through VNC for example)

In Swing overriding the RepaintManager gives such a possibility and is used (or at least was) in the VNCj project:
http://emblemparade.net/projects/vncj/
http://code.google.com/p/vncj/

Would be nice to have this option in JavaFX