Like another use said, I would rather pay once and receive updates than a monthly subscription. I know that you are using your own servers to pull information, but I don't know why that is even necessary. I would rather have an app that doesn't pass any information through a third party server.
I also ran into a problem when trying to create a milestone for a repo (this was the second milestone I was creating with the app) and it locked up.
Other than that, it's extremely nice, and if you ever made it into a one time purchase, I would probably pick it up right away.
EDIT: Just a couple of notes. I tried out a couple of other applications to compare features (since I can see how nice managing issues, etc from a single app is compared to the website) and I have to say that Ship is by far the nicest out of the bunch.
As posted below: https://www.realartists.com/docs/2.0/uninstall.html
T̶h̶a̶t̶ b̶e̶i̶n̶g̶ s̶a̶i̶d̶, w̶h̶e̶n̶ I̶ w̶e̶n̶t̶ t̶o̶ c̶l̶e̶a̶n̶ u̶p̶ /̶ r̶e̶v̶o̶k̶e̶ a̶c̶c̶e̶s̶s̶ t̶o̶ a̶l̶l̶ t̶h̶e̶s̶e̶ a̶p̶p̶s̶ t̶h̶a̶t̶ I̶ j̶u̶s̶t̶ a̶l̶l̶o̶w̶e̶d̶ a̶c̶c̶e̶s̶s̶ t̶o̶ G̶i̶t̶h̶u̶b̶, I̶ f̶o̶u̶n̶d̶ a̶ t̶o̶n̶ o̶f̶ h̶o̶o̶k̶s̶ o̶n̶ n̶o̶t̶ o̶n̶l̶y̶ t̶h̶e̶ o̶r̶g̶a̶n̶i̶z̶a̶t̶i̶o̶n̶ l̶e̶v̶e̶l̶, b̶u̶t̶ e̶a̶c̶h̶ r̶e̶p̶o̶ l̶e̶v̶e̶l̶. I̶ k̶n̶e̶w̶ t̶h̶a̶t̶ y̶o̶u̶ w̶o̶u̶l̶d̶ h̶a̶v̶e̶ h̶o̶o̶k̶s̶, b̶u̶t̶ I̶ a̶s̶s̶u̶m̶e̶d̶ t̶h̶e̶s̶e̶ w̶o̶u̶l̶d̶ b̶e̶ o̶n̶ t̶h̶e̶ o̶r̶g̶a̶n̶i̶z̶a̶t̶i̶o̶n̶ l̶e̶v̶e̶l̶ o̶r̶ r̶e̶p̶o̶ l̶e̶v̶e̶l̶, b̶u̶t̶ n̶o̶t̶ b̶o̶t̶h̶. E̶i̶t̶h̶e̶r̶ w̶a̶y̶, i̶t̶ t̶o̶o̶k̶ m̶e̶ a̶r̶o̶u̶n̶d̶ 1̶0̶ m̶i̶n̶u̶t̶e̶s̶ t̶o̶ c̶l̶e̶a̶n̶ u̶p̶. N̶o̶t̶ s̶u̶r̶e̶ i̶f̶ y̶o̶u̶ h̶a̶v̶e̶ p̶l̶a̶n̶s̶ f̶o̶r̶ a̶u̶t̶o̶ r̶e̶m̶o̶v̶a̶l̶ o̶f̶ w̶e̶b̶h̶o̶o̶k̶s̶, b̶u̶t̶ t̶h̶a̶t̶ w̶o̶u̶l̶d̶ b̶e̶ a̶m̶a̶z̶i̶n̶g̶ i̶f̶ y̶o̶u̶ d̶i̶d̶.
Either way, I will be keeping my eye on Ship because I really enjoyed it for the most part and it is better than the alternatives I found IMO. Keep up the good work!