I am seeing the first signs of falling service from Amazon now. I always loved their sales and after-sales service.
However, off late, there are too many items listed that are not fulfilled by Amazon. That means that most of them do not ship to where I stay. It really is frustrating.
They do have a search now for Amazon Fulfilled stuff, but there is just too many sellers there now.
As for Comixology, I never liked the app much anyway, but I'm in it for the free...