http://pspupdates.qj.net/3-10-OE-A-c...g/49/aid/81676

Although it wasn't said, there are options added in the Playstation emulator like new screen modes and controller port switching. Others have reported PAL games working better or perfectly.

@Gaara
The PSX emu uses the no rumble/analog controller. So no L3 or R3 (Ape Escape is out of the question) as for using L2/R2, pushing the PSP analog left acts as L2 and right is R2, but you can change the controls.
As for ease of use, I got used to the controls fairly quickly as most games I play don't require L2/R2 that much. Though the ones that do, work awesome too.