The PSP version had a bug in it that made team mates ineffective. If it hadn't I probably would have finished that version too.
Anyone thats wondering whether it's worth the burn try it out on the DS first. It's a great game and had a really nice make over for the console versions.
I played the PSP version and loved it for the first few hours, but when it started to repeat over and over and over and the enemies got more and more frustrating, I lost my interest quickly...
It's worth a try though, especially for fans of puzzle games