I think that, on its own, this manga's biggest flaw is that you can just feel that it's an adaptation of a novel. I'm specifically talking about its erratic pacing and dialogue style. Of course there's nothing wrong with that, but the fact that this never got out of its comfort zone means it's quite jarring reading something that's basically a combination of a LN and a manga.
And I think that perfectly tracks with what Mayo Chiki is as a whole. Mayo Chiki is, for the lack of a better word, a "safe" series. Nothing it does is particularly outstanding, but there's nothing outrageous, either. For example - the characters' trait follows what is already pretty standard tropes for the time. A tsundere, an oujo-sama type, a little sister, etc. Everything is predictable. Perhaps the process will turn out a little bit different from what you thought, but the outcome will never go out of bounds. What makes Mayo Chiki stands out is precisely in the process. What I truly liked the most is in the character development especially. It doesn't tumble down the pitfall that is all too common in harem media - only revolving around the male lead. The female leads have their own life story, struggle, dream that are both unique and solid enough to stand on their own, and make them feel grounded - despite how eccentric everything is in general. The male lead is reasonably proactive in his own story and has just the right chemistry with everyone around him. All the mediocre factors have just that little bit of bite to make Mayo Chiki overall a pleasant read, never a frustrating one.
So, because of that, this manga is slightly better than run-of-the-mill. Maybe even more. It's personally one of my personal favourites. Mayo Chiki's not going to turn your world upside down, but it'll certainly make your world just a little bit better.
Another plus is that all the ecchi scenes that aren't blatant (like when the female leads are just touching Jirou) aren't flagrantly obnoxious. I mean if you think about it especially considering his condition it's not too unreasonable for him to be overly conscious about those moments (I'm biased if you couldn't already tell)