Tangerine, a WPF Exemplar...
Infagistics has created this WPF application called Tangerine and they have documented a bit of the process ( requirements, architecture, lessons learned, etc.) ...
I only peeked high level through the documents, but they seem quite fair and insightful ...
I wonder if people find these references more helpful than smaller articles ala code project ... { I keep dreaming I will soon make time to write one of these ... if only I was more organized or effective with my time :( }