Please see "What's new in Visual Studio 2017" for the details about the upstream Visual Studio 2017 release, including the download information. See also the "Better Apps Faster with Visual Studio 2017 and Xamarin" for Xamarin-specific information.
This first general availability of Visual Studio 2017 comes with Xamarin 126.96.36.1994 (Cycle 9). Note that due to the new Visual Studio Installer in Visual Studio 2017 and the corresponding new way that VS 2017 installs extensions, the Tools > Options > Xamarin menu no longer includes a Xamarin-specific update menu. Instead:
Updates for Xamarin will now be found under Tools > Extensions and Updates as part of the Visual Studio Product Update. That option will launch the Visual Studio Installer program to perform updates.
VS 2017 will allow installing preview releases of Xamarin using a workflow similar to how you can install the VS Professional 2017 edition alongside the Enterprise 2017 trial edition using the Visual Studio Installer.
Please file a quick bug report using the "Visual Studio 2017" new bug form under the Visual Studio product if you see any suspicious Xamarin behavior that seems to be specific to Visual Studio 2017.
You can check the list of Xamarin issues reported by users so far that are specific to VS 2017 to see if any match. If you find a match, feel free to CC yourself on the bug report as a way to tally your interest in the bug:
(If you have reported an issue that is specific to Visual Studio 2017 but is not yet included in the list, the bug might not have been filed using the "Visual Studio 2017" new bug form.)
You can also check the list of issues reported by users so far for the Cycle 9 Stable channel versions for issues that might or might not be specific to Visual Studio 2017: