It's pretty decent. Most of the anime that started in the spring season were pretty dire (beside Hataraku Maou Sama which was hilarious) so it was one of the few from then that I enjoyed watching.
It is a shounen anime first of all and there's nothing wrong with that. It actually went from pretty interesting to pretty mediocre though for me halfway through rather than the opposite. It always had its flaws but it was still enjoyable to watch. The main characters are actually the least interesting unfortunately but some of the side cast are really good. Not really important to the actual anime but I really like the first OP too.
The biggest problem of the anime is making you care about the main storyline. Especially now in the second half, it became a lot more bland and the enjoyable part of the anime are the character interactions and the action sequences.
Again, I think part of the reason I liked it at first was probably partly due to the fact that there was only one other good show that season but it is definitely not a bad series, just a decent one with quite a few problems. It's not something I'd recommend to anyone but it's not something I'd drop either. Most of what I said sounds pretty negative but I do enjoy watching it still.
It also has the most hilarious facial expressions.