Arpeggio of Blue Steel - 9/10 (bordering on 10, but I don't like to give 10s to contemporary shows - I think a full rating requires hindsight of a show's influence on the medium as a whole, long term)
Put it simply, this blew me away. I'd had it saved up to watch in one go for a while, but I never even dreamed I'd enjoy it this much. From an excellent premise, to an intelligent treatment of its subject matter, this just keeps getting better and better. At only 12 eps too, it feels very lean compared to so many other sci-fi anime of the moment. Not a single ep is wasted.
I love that in many ways, this is essentially a harem show, but with the romantic element largely removed. It also does the whole 'these are the number of villains we'll be revealing over the course of the series, and these are there powers - oh, and we'll make you really care about them too' as well as any show out there (one of the reasons I love Bleach so much)
I like that it manages to do the whole 'oh, the baddie was defeated - but obviously they're not dead, and they're going to switch sides' thing multiple times, but without it feeling contrived.
The ending episode is stunning - I've rarely seen CG integrated into a show so well, but this looked a dream throughout, from the battles to the characters.
All in all, I'd heartily recommend this.