From what I understand (read: rampant speculation) it is a new undersized game. My guess would be that it is probably less than 10 hours in duration, somewhat like episodic content. In all honesty, Ratchet & Clank sounds like a prime specimen for the episodic model to me.
Also: Fat Princess sounds
awesome.
http://ps3.ign.com/articles/890/890482p1.html