Hard to learn, but fun to play!
This game is pretty much basic Katamari. You're making islands for animals who request them. You can collect presents and your cousins, both of which can be used in the game. Most of the animals have certain requests for their island (hot items, heavy items, expensive items, etc.) and you get points when you complete the level, but your fulfillment (or lack of) the requests don't seem to have a lot of bearing on the game.
However, you still have to hit your size requirement in a certain amount of time. You still have a certain number of minutes to get your katamari to a certain size. On this version, most levels are broken down into 3 or 4 stages, like moving from house, to yard, to town, to world, after you hit each requirement.
One of my major gripes about this game is that you tend to play the same levels over and over...I'm not sure if the items are the same or different but the layouts are the same. I guess PSP games are made for being played for shorter periods of time, but after an hour or two, you feel like you're doing the same thing over and over.
If you're a Katamari fan....pick this up, but be sure to give it an hour or two at first...it's different, but still fun.