One thing that I hope they dont change is the advertised ability to 'age my movies during night'.
Seriously I have always felt they started very late to develop the OS and included apps for the PS3 (it didnt seem tought through/decided at E3). And with no HDD I just dont think we will be able to chat, surf, e-mail on the second TV-out while someone else is gaming/watching a DVD/BR unless those apps are included on all DVDs/BRs. But I can see them delivering a DVD together with the PS3 with lots of apps.