That's really a decent price on Katamari. The game plays well on the Vita (I haven't gotten to spend too much time with it yet though). My understanding is that it's on the short side or has some DLC hook or something, but I can't confirm or deny so do your homework.
I love Katamari games and this was the first Vita game I bought and was my only game for a while. There is not enough variety in the level designs and you play through very similar stages through the dozen or so levels. i.e. the last two levels take part on nearly identical towns but the final level lets you expand into fantasy world. I did not like the touch movement controls and played the majority of the game with the traditional two stick control from the original PS2 game. There's regular, high speed and eternal mode, the last two you buy with candy points you earn in the levels.
The DLC is okay. There's a snowman level, Pacman level, collect things for money, race down a hill, etc. To unlock DLC you have to find "FAN" characters in the game (or buy them). 10 Fans let you unlock a new DLC level. One fan will always appear in the same spot of a particular level but randomly will appear so you can go 20, even 50 levels before it appears. And you still have to grab it and successfully complete the level. Frustrating and makes me want to hate the game. The Calorie level is easiest to find and capture the Fan but even online sites recommends start the level, if its not there quit, then restart until you get it.
The most boring type of level grinding. I can't bring myself to get the last 21 Fans I need to unlock the last three levels which I'll probably play only a few times.