Well, Microsoft Download Center Beta was launched recently. I only came across this today while I was uninstalling very early bits of ASP.NET MVC bits and went to download the new ASP.NET 3.5 Extensions CTP.
Their new download center is powered on Silverlight. Note that the Detailed Download pages are still typical ASP.NET pages. It's the Search results and the Quick Details Download views that are new (i.e. http://preview.microsoft.com/downloads/Search.aspx?SearchText=entity+framework).
My early impressions leave me undecided on the new search results behavior. Since it is now done in Silverlight, you lose the ability to page back through your history. Granted, their results page provides a more seamless experience without entire page loads; however, this is duplicated with AJAX. I was really looking forward to seeing more innovation, interactivity and a showcase of Silverlight power.
In any case, this will be a big step for Microsoft's quest into Flash territory. When Microsoft Download Center is brought out of Beta, you should see a dramatic increase in the Silverlight adoption rate.