hey there! Wondering what SP1 Beta 1 contains? Steve Maine details some of the WCF and WF enhancements, including some WCF "scalability improvements on IIS7". Read more on his blog. And yes, there's some WCF/Silverlight stuff in SP1 :)
Steve mentions that "we've managed to put a lot into this little release." Interested in additional details on this little release?
Read the blog posts on Somasegar's blog and ScottGu's blog who will lead you to Tim Sneath's blog for the WPF story.