It's not very good... The weapon balancing is really counterintuitive, the units are not that interesting, the maps are bland, and the story is laughably bad.
It's just a good game. Characters are interesting and maps are fun. I don't know if the story is any good since I'm skipping all the cutscenes but that bit's not important anyways.
Controls are not so good, and there are very few levels. The game gets extremely repetitive by the end. However, since it's a Katamari game it's still quite fun.
The gameplay's really good! Most of the maps are "defeat the boss", but it's surprising how each one is still very enjoyable, memorable and well-designed despite its repetitive nature.