Date published: See https://releases.xamarin.com/.
You can downgrade back to the previous Stable version by manually reinstalling each old package. See the KB article on downgrading. If you have a Trial or Starter subscription, feel free to contact email@example.com to request the older versions.
Older Mono package versions are not currently listed on https://store.xamarin.com/account/my/subscription/downloads. The Mono package for the previous Stable version ("Service Release 1") is available here:
If needed, you can also downgrade back to older versions (from before April 29) by manually reinstalling each old package. See the "Previous versions, downgrading" section on the April 29 release thread for the older downgrade links.
This first post will be updated regularly.
Hopefully this thread will help answer "what might break if I update to this release?"
If you find a new problem that is specific to this version, please file a bug report.
Please discuss older bugs that are unchanged in this release compared to the previous Stable version in Bugzilla instead.
Of course for questions and discussions about topics other than bugs, feel free start new forum threads.