Battery Life doesn't top out the Game Gear by all that much, but the lithium ion makes for fair game.
I wouldn't recommend it, personally. I bought it for launch price (which I believe it is still at) and I've used it only a handful of times. While it did come in handy on the flight out to E3 to watch Spiderman and listen to a few Mp3s.. I'd much rather get an iPod for the music experience and leave the gaming to the Nintendo systems.
And what's with the firmware crap? I purchased Virtua Tennis the other day because I love the game on the Dreamcast, only to find out I have to update firmware to play it? I don't think I'll be giving my PSP much attention in the near future. Le sigh, money lost.
Go with a DS and an iPod.