I love this series so much! I've got a soft spot for poly shipping to start with, and Kurocan does such a great job with this. I think it does shift slowly from being Rin's harem to more even — and I even appreciate the way that it's not "we three must be together at all times," that the bit in chapter 5 with the flashback to just Rin and Maki having sex was just them but not behind Hanayo's back, so to speak. (The fact that it's all hilarious is gravy.)
In other news, after years of looking at it, I only just realized that the little cat-Nanoha on the GiB translator's page has visible nipples. Huh.