About a year ago Microsoft's patterns and practices team released Acropolis as a beta - a UI framework for building WPF applications using a MVC style approach. I played around with it but to be honest I didn't feel it was advanced enough for building fully fledged business applications, but a very good start.
For the National Express project we gradually applied the MVVM (Model-View-ViewModel) pattern, which we fully crafted by hand. Obviously it was a learning experience but it worked well and fitted in well with WPF. Also as we crafted it by hand we had full control of pretty much everything going on in the application and could refactor as we pleased.
Well the Acropolis framework development project was halted about six months ago, after much user feedback. The patterns and practices team have been working on a new CAB style framework, codenamed Prism (not to be confused with Mozilla's Prism project, which integrates web applications with the desktop) . Briefly looking at it, it does remind me of the existing composite application frameworks developed by that team - namely Web Client Software Factory for ASP.NET MVP applications, and the Composite Application Blocks for building WinForms applications.
I have to say I like the approach. This feels very familar for those of us that have used either of these two frameworks, which can only be a good thing and helpful for those architecting WPF applications who have come from a WebForms/WinForms background. It will help in increasing the adoption of WPF applications for the business/enterprise.