There is something that kind of bugs me in this episode. The fact that Isshin uses the Getsuga tenshou makes me think that it's just a 'basic' zanpaktou move, and not a Zangetsu specific one. Nobody was surpised when Isshin used it. No 'how the hell did he use MY technique' type of expression at all.
If my memory doesn't fail me (and it regularly does) the person telling Ichigo the name of the move was Urahara. So either the moves are inherited, or it's a pretty standard move. Since Ichigo is (I'm guessing here) the first half blooded saiyan shinigami, it's still weird that nobody is surprised, not even Aizen or Gin.. Gin talks about it like it's the most normal thing in the world.
And if Isshin know's that 'final' version, why the hell didn't HE use it against Aizen? Even though he probably was too weak compared to Aizen, the fact that he didn't use it is weird.

I always thought that Isshin was this badassly powerful shinigami. Somehow his cape made me think he was some sort of royal guard or something. I can only hope that his powers haven't completely awakened or something, since he supposedly lost them or something.

-end of rant-