It's been well worth it in my case. Definitely go with the PSP2000 model as the Phat has an awful dpad for 2d games. The screen is ok for the games but it does have some ghosting (not nearly as bad as the Phat's). You get used to that after awhile. I don't think the 3000 model has been hacked yet, so you might want to avoid that.
It pretty much emulates 8/16bit system now. The SNES is still a little spotty in places but alot of games now run decently on it. Capcom/SNK arcade games run flawlessly as does Genesis, Turbo, NES, SMS, C64, SCUMM, and PS1. I can't seem to get the Amiga to work well though. Anyways, yes, it's well worth the effort if you want old school gaming on the go.