I thought a good first step would be to port my "Game of Life" WPF application to WPF/E and see the game run in a browser. A quick look at the documentation revealed that WPF/E doesn't support data binding, resources, or layout controls (like the Grid).
A good contrast will be to compare the following snippet of WPF code to my hacked up WPF/E equivalent. This C# code dynamically creates a "life" indicator in each cell of a grid control.
If I had $100 to spend on WPF/E features, I'd spend the whole lot on adding data binding and layout controls. Overall, WPF/E is a bit different from what I expected before I started this evening. At this stage, the technology is good for performing animations, and playing media. No small feat, really, but anything the team can add that will facilitate day-to-day business requirements (build a dashboard of key performance indicators, fill out an insurance claim form) would make the technology terrific.