A few weeks ago, our reference implementation for Prism looked like this.
Early on we decided that we needed the RI to have a better look in feel so that it delivered a more real world WPF experience. We hired a design firm to create XAML proofs based on our implementation. The process on their end was two fold. First there we a graphic designer who created non XAML proofs. Then a XAML developer converted those proofs to XAML.
Once we got the proofs, Adam Calderon from Interknowlogy (on our team) team took two weeks, and merged the new XAML into our existing codebase. In the migration, there were a few aspects of the proofs that we decided not to apply because we wouldn't push on the scenarios we need to. However, the changes we did apply, did not require much code rework to the application itself.
This is what came out of that effort, and what was in our last drop.
I must admit, I was previously skeptical of the whole designer-developer interaction and what was really possible. I am definitely now a true believer! Great job WPF team!