If you have the Beta2 or RC versions of the VS Tools for Silverlight, or the Silverlight 2 Beta SDK or Developer Editions of Silverlight 2, please make sure to uninstall these completely before downloading and installing today's release.

End users who have Silverlight 1, or Silverlight 2 Beta1 or Beta2 will be automatically upgraded to the final Silverlight 2 release starting later this month.  Until then, if they visit a Silverlight 2 (final release) site, they will see the standard install prompt that a machine that does not have Silverlight installed would see.  Clicking it will upgrade their machines to the final release of Silverlight 2 (there is no need for them to uninstall anything - Silverlight 2 will cleanly install over Silverlight 1 or the previous betas). 

Because there are some breaking changes between Silverlight 2 Beta2 and the final Silverlight 2 release, end users who have the final Silverlight 2 release installed will not be able to run applications that are still targeting Silverlight Beta2.  Most major Silverlight 2 sites plan to upgrade to the final release in the next 24 hours (which will fix this issue) - if you hit a site built with Beta2 before then you might experience trouble with it.  That should go away within about a day once all sites are updated though (this was one reason why we released the public release candidate last month - to help developers get their sites ready for the final release).