The Asp.Net membership provider has some clear uses in a web app. I am thinking about trying to leverage some of the features in a windows application (more specifically WP
Yes. Membership, roles and profiles are all features of Visual Studio 2008 Client Application Services (Services tab of a project properties)
http://msdn.microsoft.com/en-us/library/bb384297.aspx
http://channel9.msdn.com/posts/DanielMoth/Client-Application-Services-with-Visual-Studio-2008/