From the KB Article:
This update improves stability, media streaming, and the auto-update component. This update also improves support for Mozilla Firefox 3.
I’m still hopeful that Silverlight 2 RTM will have a Trigger construct of some kind. But I’m convinced ElementName bindings, Data Template Selectors, and Markup Extensions won’t come until 2.5 or 3.
I hear that ElementName bindings will be added in the RTM… as for the other stuff, probably not!
I have a quick and dirty solution for ElementName bindings within XAML – http://neilmosafi.blogspot.com/2008/05/silverlight-2-creating-bindings-between.html