This thread has now been closed to direct all further updates about this release onto the latest announcement:
Please see https://releases.xamarin.com/alpha-release-15-2-alpha-preview-3/ for the details about this release, including the steps to update or downgrade as needed.
Using the latest Visual Studio for Mac Preview 8 with this release is encouraged, but you can also continue to use Xamarin Studio if you prefer.
Please file a quick bug report using the "15.2 Preview" new bug form if you see any suspicious behavior in these versions that you wish to report.
Comment in this forum thread if your question is not related to a suspicious behavior after download, but instead one of the following:
EDIT Apr 11: Update link to Release Blog post for new versions.
EDIT Apr 12: Update information about the release availability for VS 2017.
EDIT Apr 19: Update link to Release Blog post for new versions.
EDIT Apr 20: Add information about VS Preview 15.2 (26419.01 - Preview).