Bryant has a new WPF/E sample on his site. This is a WPF/E remake of the Kevin button (I was actually just hanging out with Kevin at the Tech Ready ask the experts). This version uses the new WPF/E downloader object which has a similar API to XmlHttp, includes download progress and works exactly the same on every browser. Click the image below to run the sample and check out Bryant's blog post for the code.
The one thing I still don't get: how is this a button? :)