Yeah, I agree that it's one of those "okay" shows. I was good with renting and watching it, but I own Romeo X Juliet and I wouldn't switch the positions of the two. Of course, Romeo X Juliet beats a lot of competition, but I digress.
I think the general concept is quite good, but I have to agree about the execution. Ayano's too hostile, too much the "tsunadre" stereotype. In one scene she'll be pretty decent, albeit normal. But in the next, she'll be the victim of comic relief. This makes her look rather foolish at times, which can make it difficult to take her or her attraction to Kazuma seriously. Not that I didn't see some chuckle-worthy moments, which I did. But so far Kazuma's basically always the smart one, which makes their encounters predictable in a way that they shouldn't be. This is what happens when you write personalities instead of characters.
The action definitely suffers from the animation's limits. Fate/Stay Night action this isn't, especially with the tendency to have villanious monsters take a more prominent role than enemy magic users--so far, anyway. At least they don't use the stock animation for Ayano calling her sword in every episode.
I thought the Ren/Ayumi story was definitely the best one. Even if it was predictable that everyone would team up to attack the real problem, it was ultimately tragic and the characters were also basically outmatched on their own, so it isn't like the Kazuma/Ayano/Ren trio can beat anything and everything. This is good, since the show would really be completely boring if they were always coming out on top. They also did that with one or two of Ayano's fights earlier.
The middle, I thought, was the worst. I mean the Misao story specifically. Her psychotic turn seemed rather arbitrary, and didn't sit well with me even though she was being influenced to a massive extent. I'm not saying she had no reason to be upset, but the things she did were off the chart. Then at the end she's shown a lot of mercy, all things considered. Now I suppose that's the good thing to do, but in reality she would be arrested. It's also not clear to me that she's even out of the family, which I think she definitely should be.
I get the sense that a "big" plot will manifest itself in the second half, so maybe the series will really pick up at that point. But yeah, I agree, I wouldn't write it off but I definitely wouldn't call it a must-see either.