Haven't read all the replies but on the topic, buy a GP2x because it has raw power for other than, you know, 3D fluff racing/shooter games.
It really has the potential for mindblowing 2D pixel wizardry with those CPU cores. Some stuff realize that potential, many don't, yet. You won't see innovation on the PSP, because everyone will use that 3D chip and port lofi versions of better 3D games.
I looked at a PSP before the GP2x cos I wanted to play Mercury
What made me switch was
1) TV-out ! !
2) ffs... all that runs on 2 AA batteries, mindblowing!
3) hated the PSP sliding button type analog joy that made my car swerve like crazy and put in a stupid place
4) hated the blue ghosting of the PSP screen
5) when PSP gets replaced by the next hot thing, the open GP2x will keep developing
my 0.02 Euro