I have to wonder about Ishin's battle capabilities. He somewhat mentions that he isn't at his 100% after regaining his power at the time of the Arrancer Grand Fisher's attack. Then later on in Karakura Town, he quite easily handles Aizen (who is pretty much 2x a Captain's power), even forcing him to his knees without sweeting much. For him to be forced to only defend against that Hollow, would suggest that it's battle capabilities far surpasses that of a standard Captain-level Shinigami. Assuming that Ishin hasn't become much stronger after his fight with that Black Hollow until the point where he discarded his power.
Anyway, this page:
seems to be referring to something important, if we assume that by living creatures, Azien means living humans, then it might be referring to what Misaki did or wished for (then again, only Urahara's H-cube had originally a mind of it's own IIRC). Though it might simply refer to the potential that everyone holds, that can reach even that of the Soul King or something like that (still, why would Ishin be pissed by it so personally ?).
I'm still wondering about Urahara. He created many things, he even was able to create the H-cube. He lost it, but he couldn't control it anyway, in the past that is, since he suggested that he would be able to do it now (http://www.mangapanda.com/94-51305-9...apter-402.html). Seeing as he is able to control it now and was able to create it in the past, why didn't he make another one ? Did he really seal it because of the fear of it's power, or was he preparing himself in order to take total control over it ? Well he seems to be OK with Soul King ruling all, but he still seems quite fishy.
EDIT: Hm, I wonder if this means that the anime spilled the secrets right at the first episode :