Nicholas Bishop has uploaded a series of screencasts demonstrating the work he has done on Multires for the Google Summer of Code.
See the all current screencasts embedded after the cut. I've included Nicholas's descriptions from Vimeo describing what each video is demonstrating.
Or if you'd like to browse each video individually you can find them here.
The above shows an example of the new multires modifier; shows sculpting on the multires mesh, then the base mesh is modified; the modifications are then sculptable as well.
Note that it looks a bit funny after the extrude, because the sculpted data is just being copied to the new faces. In this case it would be better for the new faces to be "blank".
"What happens if you delete a face?"
Pretty much what you would expect
Subdivision works better now; displacements are properly subdivided.
Multires modifier with an armature modifier. Showcases my expert rigging skills.