From what I've seen of "Oslo", the new "M" language for creating Domain Specific Languages (DSLs) is the part that seems most mature (even though it's not even in beta yet). Josh has two sample video's showing a DSL creating XAML and the second one shows how to write "plain english" to create a WPF application. Really cool demo!

Speaking of XAML, there has been some buzz about the next version and it might be getting some more momentum than just beeing something for WPF, WF and XPS. I think that I need to do some catch up and watch the XAML presentation (first and only so far?) from PDC.