My larger issue is that the UI gets tweaked constantly. To the point where the app you originally purchased and the one you're currently using may not longer resemble each other and there's nothing you can do about it when it's hosted.
This is a big problem - you are right. Users don't like things changing either. It ranges from a few minutes to adapt to throwing toys out of the pram and having to be retrained on something minor. This is an unfortunately reality.