Out of fear of sounding like an utterly obsessed nitwit, I'll refrain from typing too much.
When I started this series, I didn't have particularly high expectations--I stumbled across it almost accidentally, after seeing people mention this along with Aoi Hana and Husky and Medley (HasuxMedo). I'd seen it and heard about it occasionally, though the synopsis didn't draw me in much. And then I gave it a try. The beginning's adequate, and kept me going long enough for me to reach the seriously brilliant meat of it. The characters start out simple, with quirks that you won't really notice, and then they blossom or reveal themselves to be characters written with depth, clarity, and a host of personality and engaging backgrounds, some of which tie back amusingly to those quirks in the beginning, and really flesh them out. Pretty much every character is like that; perhaps tellingly, my opinion of Tomoe Hachizuka changed drastically after chapter 19. There's a lot of depth and content to this manga character-wise.
Art is great. It takes a chapter or two for the mangaka to settle in on the style of Sumika (her bangs change a bit over the course of it), and the characters get smoother and smoother lines. When it oscillates between serious-style and chibi-er-style, it's done very well.
A further testament to the well-written side of this manga is the plot. Though it is a bit slice of life-y in the start, appropriate flashbacks, character examinations, and good pacing really give a strong sense of purpose to the manga. It actually feels like it's going somewhere, even if it's taking its time like a chill turtle (as yuri manga are wont to do).
Another unique point for this manga is that it attempts to portray lesbianism/crossdressing with more realistic aspects in mind. Granted, it isn't total realism, but there's noticeable negativity/prejudice present in it, and it does affect the characters. The way it portrays it manages to be smooth enough so as to not cast a bad light over any particular group, but rather shows it as a part of life, and again, is well written.
So there you have it. It's a great manga for pretty much anyone (provided the anyone doesn't hate same-sex relationships or the sort), because of the writing, the pace, and the likable (yet flawed) characters. I'd recommend it.