I'm in the other boat. There were a TON of great RPG's that I missed out on with the PS1, and those that I got to play, I want to play again. I bought Wild Arms the day it came out on the PSN, and the fact that those games work on my PSP is just godlike. I can move the save data back and forth between my PSP and PS3 and play any which way I feel like.
At $7 you'd be a fool to miss out on some of the best rpg's ever created, plus, as awkward as it is, PS1 games LOOK fantastic on the PSP :P Sadly in terms of graphics they look (to me) sooooooooooo much better than anything I've ever seen on the DS.
And I don't know what's wrong with me, maybe I have become a graphics whore or something, but there is literally nothing on the DS list that looks remotely interesting >_>;;; I keep hearing about what a "powerhouse" the handheld is, but everything on it just looks so terrible to me >
From 0 to KICKASS in .stupid seconds.