I have read all available manga at the point of writing this (vol 14). Its a high ecchi harem story with monster girls. First without spoilers it has a semi weak story as its mostly set up these characters meeting and interacting with one another, which is the main enjoyment is the humor. It doesn't try to be much more then a funny manga with crazy character designs but at times does bring up some interesting stuff like immigration, mortality, and other subjects with these characters with humor (see spoilers for examples).

CONS
The characters personalities are simple at first in it but can be seen the writer probably took constructive criticism on that matter and tried to fix it with a decent amount of success once you get past where the anime and OVA's end as they get more aspects start to shine through (the anime covers up to vol 6 only). The story is simply to prove a human can have a functional romantic relationship (and later marriage) by using the main character as "test study" but i found that the simple fact all of these characters living together without the characters murdering each other or fighting tooth, nail, hoof, and claw when living with a male who is a common romantic interest proof enough that a full integration of all the races can be done, which should be a more important matter. Also i got really annoyed with the laws saying humans cant ever harm a non human or vice versa regardless of self defense or otherwise which makes no sense at all. Heck it even got in the way of cops dealing with a issue with Orcs in a scene as they "were not allowed to use force" when the orcs have hostages and firearms so makes no sense.

PROS
This series is very fun to read just on seeing the next interesting character or race to come up and the most fun part for me is the tons of nods and references to everything from American horror films like Final Destination to video games to Godzilla and kaiju battles to George A Romero fans and the feels towards running style zombies as one character said "fast zombies are okay, but give me a proper shambling horde any day!"." Those of course are the pros beyond the fun art and funny ecchi scenes. The main can be a pro or con depending on why you look at this as hes simple but clearly a honest and likable guy along with him clearly liking all of them (hes in essence a honest and kind guy while having no problem looking at the girls "assets" sometimes) so works well as a character any male reader can imagine putting themselves in his position in.

SPECIFIC SCENES I WISH TO MENTION (Partial spoilers ahead)
There's a few scenes that it does something smart in that i wish to bring up to show this is not just silly ecchi fan service and humor even though a lot of it kinda is. The most common of them being about immigration of these races and even of a few of them should be considered even sentient for the races like slimes as they technically don't have a brain and one of the main cast is one. Also a very specific scene with a character named Lala who she always talks like shes the grim reaper herself as shes a Dullahan (in essence a headless horseman style being) and was talking as such in a hospital around a group of kids staying there which lead to a very somber moment for her as a character as one of them was dying. This scene stands out as the best scene in the entire manga hands down so i wont spoil it.

So ya its fun, enjoyable but nowhere near above any kind of criticism even though its one of the most fun manga i have read