It’s installed and available right now on all of the IIS8 servers. If you want to use Core but your site is on an IIS7 server, we can migrate you to IIS8. Just let us know.
The only known issue at the moment is deployment only works into your root directory. We’ve let Microsoft know that there’s an issue deploying to a subdirectory, and we expect that they’ll fix that in a future release.
We’ll be publishing some posts soon on developing with ASP.NET Core 1.0. Stay tuned.