Just got a PSP-3000 recently, and thought I should comment on it a bit.
Unlike the PS3, only one account can be active on a PSP at a time. The PS3 can have more than one. I think Sony should have this fixed; it would lessen the trouble with people converting to the PSP Go, as there are people who would like to have content from both the US and JP PSN stores. Even if it means a PSN account can only activate 1 PSP at a time, being able to have multiple accounts active on a PSP would be really nice.
Speaking of which, multiple profiles on the PSP would be nice, just like how we have it on the PS3.