Unfortunately something similar happend to me on the PSP too. Ratchet and Clank - Size matters is the only Ratchet and Clank title on the PSP until today. It is a very good PSP title, still it has some things that bother me. First of all, hence the lack of a second analog stick on the PSP you'll have some issues with strafing, controlling the camera and shooting at annyoing enemies at the same time. At some points it feels like you would need a 3rd hand to do all this at once on your PSP. Next thing is the same problem all Ratchet and Clank titles have in my opinion, even fully upgraded weapons from the early game, in which you invested lots of bolts, are useless in the end game. You wish you hadn't bought all this crap in early game because you could use the bolts now. Also there are too few checkpoints in the levels, at some points you'll have to play almost half of the level again, because just few steps before the next checkpoint is some frustrating fight.
I am not sure if the frustrating moments are there because they are just frustrating or because the controls on the PSP lack some comfort which the bigger brothers on the PS2 and PS3 have.
+ Nice visuals
+ A solid PSP Jump n' Run title
- Frustrating at some points