User blog comment:BlazeUchiha/Aizen's New Form/@comment-1712587-20100521103911

I think that now he has "reached the limits of his shinigami self" he has just started not registering things like pain. It seems that his ego is so massive now that anything like that is now beneath him. He can't possibly imagine someone being able to do any damage to him so he can't even see that he has been attacked now.

I think it's all in his ever increasingly overblown ego.