As we close down on the release, we're actually pushing out an update to the Silverlight RC build in the next couple of hours. The update is Sunday night's drop - build 20730 (the last release was 20724), and I'm going to informally dub it "RC2" for ease of reference.
This is one of a few critical updates that we'll be pushing down over the next couple of weeks to test the update mechanism. If you've set your update options to prompt on install, you'll see a dialog very like the following when you next visit a page that contains Silverlight functionality:
All updates will require a restart at some time to take advantage of the functionality changes. All prompted updates can be “postponed