Well, after a few years wait—in which I kind of forgot about Y, figuring I'll get to it eventually—I finally finished the series, reading the last two volumes just last night.
It was a fairly satisfying ending, particularly considering how badly it could have ended (the cover of the last issue really had me fearing the worst), and the fact that after so much suspense and build up, there wasn't really an explanation for the "gendercide" and a way out of it that would have lived it up to the mystery the first two-thirds or so of the series suggested (I would have liked a better explanation for the death than we got, honestly, but it wasn't a terrible explanation or anything).
And God, what a climax to the book. I—and everyone who read it—saw an aspect of the climax coming, but certainly not the exact way it played out. I'll admit, part way through the tenth volume, I was pretty emotionally devastated, and felt close to tears.
Specifically, when I read this panel:
Say it ain't so Agent 355! Please, say it ain't so!
