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: http://talk.maemo.org/showthread.php?t=80644
CSSU features app: http://maemo.org/packages/view/cssufeatures/