I am half through...in some short words:
If you like the Dark Forces/Jedi Knight series and you can live with some issues (frame rate, controls) get this game.
If you believe a PSP game has to look and control as good as a home console game, you better get something else (or no PSP at all)
Pros: Pretty diverse gameplay and levels/locations, controls OK with analog stick moving and lock-on fighting, looks nice
Cons: Frame rate issues (and I am not a 60fps whore), controls are far from perfect, typical PSP graphics problems (textures mostly), some minor problems that could have prevented with a little more time, cutscenes use ingame graphics (ugh)
Overall: I am having lots of fun with it. Most times it feels like a "full-grown" version, just sometimes it does not (less weapons, a little less polish and the other issues)