All the goodness of Katamari, now hand-held.
Anyway, as for the actual gameplay, I have to say that the PSP isn't best suited for rolling a katamari. Because buttons have to be constantly held, you'll quickly find your fingers becoming sore when first playing the game. And also because of the the lack of the conventional joysticks, movements are somewhat harder with just 8 directional buttons, although it still works. I miss the ability to quickly turn by pressing down L3 and R3 at the same time, which is not available in this game (for obvious reason, although it would've been nice if they assigned it to some other buttons).
Also because of limited hardware capacity, there are only a few maps in the game, used over and over again, and that can become quite boring after a while. However, there are a lot more wearable gifts, and more interesting cousins to roll up.
Overall, very fun, worth your money, buy it :p