I like how this thread has turned into a general current-gen handheld discussion.
On that note:
I think the PSP and DS work best when they embrace their "handheld" functionality and don't simply try to be portable consoles. The DS, due to it's limitations, doesn't really have that problem, but what BORES me about the PSP is that too often its game developers try to replicate experiences from the current-gen consoles, and the results are very hit/miss. God of War: Chains of Olympus was a good game and looked great, but too many concessions had to be made to recreate the gameplay on a device less comfortable and with fewer buttons than a PS2 controller.
Both systems shine their brightest with original titles that are built from the ground up with the exact platform in mind.

