I just finished the series tonight, so I'll share my thoughts while they are fresh in my mind: The pacing and the characters were excellent, and it definitely held my interest- but 2/3s of the way in it suddenly became a very obvious Fullmetal Alchemist X Harry Potter fanfiction sweatdrop Think, "What would it be like if LUST was the headmaster of Hogwarts!?" and you've got this story. Still, for as much as it borrows from other series, the original content is truly excellent. I think an 8/10 is fair. For those who want spoilerific justification to my rating, then read on:
Miss Ricketts was one of my favorite characters, and I don't like how we never find out what became of her once she was put in the child's body. I mean, I guess we're to assume that the windmill children keep her prisoner with Miss Weaver forever, but Lucy had wanted to get that child's body back, so... what happens if they do find Ricketts, with the machine being broken and everything? Also, 'Great Gears' was mentioned a few times, but never elaborated on. It was obviously a scrapped plot point, but it feels sloppy. In any case, as for the Harry Potter and FMA elements I mentioned, I don't want to be judgmental, because for all I know, the author might never have seen either one, but you'd have to be blind not to notice the Harry Potter themes - right down to the designs of the school, its uniforms, its "away from the world" nature, class structure, and orange haired Lucy being paired with dark haired Claude. Not to mention when the windmill children break loose and fly around the school in their tattered robes, it looks like a death eater scene pulled straight from the movies. As for Fullmetal Alchemist- this is more subtle, but the principle looks EXACTLY like Lust: the hair, the breasts, and the extending sharp finger nails to boot. Not to mention her "big experiment" involved transferring souls to metal objects, and other human's souls into new human bodies, even when this series is supposed to be about "Mad Science", making the swapping of brains a much more logical choice.
Update: The 4th volume, which is really a sequel of sorts called "The Perfect Cog" is pretty lousy. Probably since all the interesting characters with the most personality from the first three volumes are not present....