Like Beta 2, the RC is a  supported, "go live" release, able to be used in a production environment.  If you already acquired your support ID for Beta 2, it will continue to work for the RC.  If you haven't gotten it yet, here's how you can: http://blogs.msdn.com/bharry/archive/2009/10/26/support-for-vs-2010-beta-2.aspx

Brian