The PSP is great, especially if you import titles. As a fan of RPGs, some titles you should check out are:
Metal Gear Ac!d
Tales of Eternia (EU)
Breath of Fire 3 (EU)
Just some decent overall games for the PSP:
Winning Eleven 9
Guilty Gear XX (Import)
It's still kind of pitiful compared to the DS, but it's not like the system is bad in any way.
I kind of disagree, since I've found more stuff I liked on PSP, compared to DS; however, I do still enjoy both.
There is the Popolocrois port(/remake?) too, I thought that was a nice little RPG.
I thought the game was awesome. Originally, it was my favorite PSP RPG, until VP Lenneth came around. Definitely very underrated IMO.