Vertigo made a reference application for Microsoft, using WPF and Silverlight, called Family.Show. It's a nice looking and very easy to use genealogy app which has all the features you've come to expect from a WPF tool – zoom, move, animate, shadows…. You name it. Source code is available too of course.
Nice thing is it can handle GED files, which is a weird but common ASCII format for exporting and importing genealogy data.