The opening and animation are really good, and the voice acting is great too. The introduction for Renge was quite adorable, it reminded me quite a bit of K-on.

There's way too much going on, though. The battle scenes feel slightly out of place, with all the camera angle movement and the choppy CGI. The pacing is also a bit erratic. It picks up considerably during the first half and mellows down quite a bit during the second half.
I'm guessing this is not the type of anime you might wanna watch if you crave consistent pacing and airtight logic. More like the kinda anime where you stop trying to reason with things, sit back and embrace it for what it is.