Well I bought one off my friend who just wanted to get rid of it, for 40 dollars.  That being said, its an excellent 40 dollar purchase =P

Pros: 

Can emulate just about anything from (NES, GENS, SNES, PS1) the list goes on

Better graphics than the DS

Maybe less laggy netplay, but that depends

Can watch converted AVI videos with far less hassle than doing it with the DS' R4 device

Cons:

Bad game library save a few (FF7:Crisis Core, Tekken DR, FF: Tactics, Star Ocean First and Second)

Controls feel incredibly stiff (I'm a fighting game fan and playing Tekken: Dark Ressurection on that thing is a pain)

Horrid battery life (Maybe your mileage will vary here, but mine is like 2 1/2 to 3 hours of play.  My DS however, is anywhere from about 5-8)

Screen feels incredibly vulnerable to scratches and damage and in turn the whole system feels like you should treat it REALLY gentle.  Feels way too fragile.

All in all, I guess it's not a terrible handheld.  I really think the Nintendo DS has TONS more to offer.  But the problem I have with the DS is this.  For every amazing, awesome game… 18 Imagine Babyz come out.  I'd say if you're really bent on picking the PSP up, read up on some reviews.  It really has a lot of power behind it and can emulate tons of stuff, thats why I really like it.  But in all honesty, when you're playing emulators instead of playing games, than is it really worth it to own the PSP if you're not using it to play PSP games?  I don't know, I'm gonna keep mine around even though I constantly wavor in and out of wanting to sell it.