Here is a great video review showing some of the features of the stable CSSU 21.2011.38-1Smaemo3 update from May 2012. The video is by Divagantegouveia.

I am particularly impressed by the speed of phone switching between horizontal and portrait mode and the locking of screens between portrait and horizontal mode.

Video Source: Youtube
Custom hildon-desktop:
CSSU features app: