We strive very hard to be backward compatible as we've realized that our API is used in sometimes unexpected ways. But, in order to make new changes, sometimes we need to deprecate and drop old features, API, and tweak request and response formats. To enable this and give you sufficient time to adapt to the changes, we are adding the Deprecation Notices section to our documentation website.
Also we've started to add Changelogs to the Payment API Releases that impact the merchants, so that you can track the feature requests you've been looking forward to.
As usual, please contact firstname.lastname@example.org for features requests and concerns with our API and deprecation plans.