For an detailed user-level description of new features see the following blogpost:
http://code.blender.org/index.php/2012/05/node-editing-tweaks/
TL;DR:
* Frame node gets more usable bounding-box behavior
* Node resizing has helpful mouse cursor indicators and works on all borders
* Node selection/active colors are themeable independently
* Customizable background colors for nodes (useful for frames visual
distinction).