I only gave this a high rating (yes, 6/10 is a good score from me, for a romance series) because of the absurdly gorgeous cast. My utter joy at finding a yuri manga where the characters have faces appropriate for their age and beautiful, well-proportioned bodies (instead of the faces and figures of 10-year-olds embellished with gigantic breasts and abnormally wide hips like in the majority of GL) superseded everything else.
There are comments here that claim this manga's more like BL than GL... Really? Those look like boys to you? Pfft. And the decision to use male pronouns for the Adams and female ones for the Eves was the scanlators' choice, since the English language doesn't have respectful gender-neutral pronouns. Also -- yes, there are girl x girl intimate scenes. Good ones, too!
As for the story: the world building is nicely done and even makes an odd, twisted sort of sense, but the development of the plot is practically non-existent. In the end, the interesting premise was merely a gimmick to showcase gender-bender shenanigans and sappy romance, which probably doesn't come as a surprise to anyone who's ever read a GL (or BL) manga that purports to have a non-cliche setting.
If you're like me and are sick to death of seeing elementary-schoolers with watermelon boobs and tomboys with underdeveloped bodies, and want some really lovely figures for a change, give Renai Idenshi XX a try. But if you were lured here by the synopsis and hoped for something less shallow, story-wise, than the average yuri, you're in for a huge disappointment.