I have been looking at the MVVM with rx integrated.  UI in general is Async, in that it is a STM be it GDI or WPF.  It is also highly event based so it makes sense, at least for me) that RX would be a good glue to allow compostion. 

The one I am looking at is http://blog.paulbetts.org/index.php/2010/06/15/reactivexaml-a-compelling-combination-of-mvvm-and-reactive-extensions-rx/

 

Although, there have been several discussions on stackoverflow and general musings accross the net. 

D