Please see https://releases.xamarin.com/stable-release-cycle-8-service-release-0-w-xcode8-1-support/ for the details about this release.
Please file a quick bug report using the "Cycle 8" new bug form if you see any behavior that looks suspicious in these versions (and if it isn't clear whether one of the known issues in the release notes matches the problem).
Comment in this forum thread if your question is not related to a suspicious behavior after installation, but instead one of the following:
Apart from the specific adjustments for essential Xcode 8.1 compatibility, the known issues in this release are unchanged compared to Cycle 8 – Service Release 0.
The Cycle 8 – Service Release 1 version currently in the Beta channel includes additional fixes for those known issues, but it has not yet been updated for Xcode 8.1 compatibility. The Xcode 8.1 compatibility changes are in the process of being added to those builds for a refreshed Beta version as soon as possible.
[Xamarin.Android] - 46279 - "C:\Program Files (x86)\MSBuild\Xamarin\Android\mono-symbolicate" store-symbols ... "obj\Release\android/assets" ... exited with code -1073740791" and "Assertion at ..\mono\metadata\class.c:5078, condition `class' not met" when attempting to create Android packages in the Release configuration.
Edit Nov 01: Add known issue 46279/46164. Remove note about outdated Beta versions. The new Beta versions from today include the Xcode 8.1 compatibility changes.