If you're a fan of the series then this will be kind of like watching an OVA, with a lot of art both ingame and unlockable, and the voice actors all being present.

As a shmup, well... the game gets pretty frisky at high difficulties, and there is also a modifier to get more score at the cost of damage taken; this can mean you will be down in two or three hits depending on the characters and they barely heal.
Luckily... your time isn't really wasted due to the fact that the achievements require a lot of grinding so there's always some progress you're going to do. But now you have to grind a lot...

Ultimately I had fun with it. You should probably get it on sale tho.