Form the below article we can say that the PSP2 will have the following feature/ non features
Sliding Screen
NO UMD drive
Will allow shoulder button games when closed
screen similar to PSP 3000
http://www.eurogamer.net/articles/developer-backs-up-psp-4000-chatter
Now if they make it like this I know I would want one instantly. Whatever Sony it will be hard to make it look more impressive then this.
PSP 2?
No UMD is great in some ways, i.e Less loadings etc. But what about the back catalogue. Possibly downloadble through PSN. And so on.

