There's a presentation here from Dec 6 on 'Advanced Graphics Techniques for Playstation Vita' - not at all sure if it provides any new insight on the hardware side, but in case it does, here it is:
http://research.scee.net/files/presentations/gceurope2011/VitaIactaEst.pdf
On a more software-y note, it gives an overview of deferred rendering on Vita using Uncharted as an example - kind of surprised it's using that given that the PhyreEngine presentation from GDC wasn't very optimistic about deferred rendering on Vita.
Anyway, enjoy
http://research.scee.net/files/presentations/gceurope2011/VitaIactaEst.pdf
On a more software-y note, it gives an overview of deferred rendering on Vita using Uncharted as an example - kind of surprised it's using that given that the PhyreEngine presentation from GDC wasn't very optimistic about deferred rendering on Vita.
Anyway, enjoy