I've spent some time looking at the Vertigo WPF reference application Family.Show. It's a really cool application, while I was playing around with it Rebecca saw it and immediately wanted it installed on her computer, she's been busy entering data into it. I hope an open source community forms around it.
The most interesting thing I found was a presentation by Scott Stanfield at Mix 07, he describes some of the lessons learnt from building this application. From the sounds of it the problem domain caused the bulk of the problems. It's certainly a testament to the design of the WPF that guys who have never used it before can produce something so stunning and the code is very nicely laid out.