I was slightly disappointed in this chapter. It starts out with a nice little fight between Aizen and Isshin which would have been nice but all anyone wanted was to see Gin's bankai. When we finally get it it turns out to be nothing but a longer shikai. I knew it was not going to have to do with a fox or a snake like everyone though but come on! It's a bankai, it is meant to be impressive. Byakuya had just a larger form of shikai for his bankai but it is awesome due to its many different forms.
I hope that Gin's bankai turns out to have some special abilities but right now it does not seem like a real bankai. Every other bankai has some special ability that makes it hard to beat. Byakuya, gets his million blades and many forms, Renji gets a giant cannon, Soifon gets a giant rocket and even Ichigo gets incredibly fast. Right now, all we know is that Gin's bankai is much longer.
In the next chapter, I am hoping we get more of an insight into this and I think we will. Even when Ichigo stopped his attack, Gin was still smiling. This clues me into an ace up his sleeve, whether or not this is a special bankai ability or not will hopefully be seen soon. I know Kubo likes to jump around a bit in his writing but I am really hoping he keeps a focus on Ichigo vs. Gin for a while instead of switching between that and Isshin vs. Aizen. I am very interested in that fight as well but I want to see one play out before we go to the next.
Edit: Possible theory, Gin may kill Aizen after all considering the name of his bankai.