I'm actually playing this on my PSP right now, and I must say it is a bit addictive, especially compared to the plethora of PSP games I've tried lately that were anything but. Like most dungeon crawlers, it was pretty tough to get started (though nowhere near as tough as Class of Heroes, I had to start over 3 times just to get a decent foothold in the first dungeon, some of the monsters were strong enough to 1-shot my party and didn't drop enough cash to pay to resurrect them) but the pokemon-ish aspect of "capturing" followers is pretty fun. Although 10 hours in, my followers don't feel anywhere near as powerful as I think they should. That and the "random" synthesis failures that seem to claim all of my best materials. The game has spotty voice acting that, to be honest, is more of an annoyance than anything else, plus I just can't see the voices matching up with the characters that are speaking.
Overall, I'd say it's a fun game. Is it $30 worth of fun? Only if you're a fan of the genre. If you don't know but think it looks fun, try out Shin Megami Tensei Strange Journey on the DS first.