The release candidate for Silverlight 5 is now available for download over on the Silverlight.NET site. You can go there directly;
or, alternatively, pop over to Pete Brown’s blog where he’s got a write up;
including a number of links to posts that Pete’s updated from the beta to the RC.
One thing I’d say is that there isn’t yet an updated version of Expression Blend for this RC and I believe that the existing “Expression Blend Preview for Silverlight 5” that you might have installed will not work with the updated bits so if you’re wanting Blend support then it might be worth waiting a little for Blend to get in sync with Silverlight.
I’ll be trying to catch up with the RC myself over the coming week or two.