In response to the original question, this article in SDTimes describes the experiences of one top design house as they built their first WPF application:
http://www.sdtimes.com/article/story-20051115-10.html

These comments aren't unique - another design house commented to me just yesterday that they were trying to encourage clients to adopt WPF because it would mean that the designers could achieve far more impressive results in far less time.

Given how early we are in the product lifecycle, this kind of feedback is encouraging...