Tim Sneath's post Our First WPF End-To-End Reference Sample: Family.Show caught my eye today, and boy am I glad it did.
I have to admit from what I've seen Microsoft and Vertifo Software have done an outstanding job on Family.Show. It is definitely more than a demo, I'm not sure reference application does it justice.
You can install and run it using ClickOnce, btw. :) Source code is available. Be sure to check out the lab to see more projects.

"Microsoft and Vertigo Software launched of a brand new end-to-end reference sample for WPF."
"Available for download immediately, Family.Show is a genealogy explorer that allows you to create or import a family tree and explore, annotate or save it to XPS."
"Our designers employed every trick in the WPF book– styles, resources, templates, data binding, animation, transforms– to present an innovative visualization of the classic family tree, freeing our developers to concentrate on behind-the-scenes features like XPS, P/Invoke wrapper for Windows Vista common dialogs, and ClickOnce for WPF."
