That depends on where your definition of "really good" lies. I'd give it 4.5/5 for fun fast shootery action, which makes it a must-buy due to the criminal shortage of shooter games on the platform.
Be prepared that it's somewhat language-intensive and though cutscenes can be paused while you look up words in the dictionary, that's a messy way to play (because that's how I'm playing, my Japanese is pretty blah).
It also supports the Circle Pad Pro =)