VS2008sp1 Beta contains XML Schema Explorer written with WPF
I've blogged about this back when it was in early CTP. Now, I'm happy to see that the XML team has shipped their WPF based XML Schema Explorer in VS2008 sp1 beta. See "New XSD Functionality in VS 2008 SP1 Beta".
It is nice to be able to say that part of VS is built with WPF...(beyond the WPF Designer bits which had to use WPF).