I beat the game a little while ago so here is my review
gameplay
The gameplay has a lot of variety and is a lot of fun. You get to do different things like a very fun skiing level. Plus the fact you can play as different characters like Ratchet, Clank, Captain Quark and the gadgetbots. I was very impressed by the gameplay and it's variety.
graphics
This game has great graphics. The detail in each level is amazing. Everything has a lot of details in them from enemies to the landscape in the levels.
soundtrack
This game includes a very nice soundtrack with music that varies by level giving it a very unique touch in every level and every challenge.
controls
The controls were very smooth and easy to use from playing as the different characters to the different challenges. the only time I had problems with the controls were the rhythm challenges when you had to press certain buttons DDR style. At one point I feel the buttons just go way too fast but once you get the hang of it even those challenges were fun.
storyline
I won't go into the specific story so I don't spoil anything but I will say that the story was very in depth and keeps you drawn in. It was not at all completely predictable like the story in Size Matters. There as only one thing I really saw coming.
Overall
This is a great PSP game and a must own for any of the ratchet and clank series and a great improvement over Size matters. I give this game a 10/10