If you're into good RPG games, then yes, it's worth getting. I've played Valkyrie Profile: Lenneth, which is a really good classic that's revamped for PSP, and right now, I'm in the middle of the spanking hot Monster Hunter Freedom 2 (I've reached the stage in MHF1 where I can't play alone anymore).
Only real draw back is the online game play that requires WiFi Max or something that allows your PSP to be hooked online to play with people across the globe. But I've got friends to ad-hoc with so the multi-player concept is still there. And it's nice to sit at McDonald's with just a small bag of fries and simply play. Perhaps the main feature that really gets me happy is that I can play whenever and wherever I want in any time period - maybe you could kill 5 minutes when waiting for a friend to show up somewhere and can still switch off without saving and turn it back on to back to where you left off.
DS games tend to be more cute, but sometimes there is only so much girly cuteness I can take.
Your choice.
- Amantis