Here's an interesting look at how User interfaces (or user experiences) come to fruition, and how difficult it can be going from an designer's vision to actual implementation. In this video from a Win CE presentation at Computex in Taiwan, there's talk of bringing better tools to designers to lessen the load on developers.
Without getting too terribly technical, let's just say that there's a good possibility that we could see some of this stuff future versions of Windows Mobile. You'll recall that Windows Mobile is based off CE, so we're not quite talking apples and oranges here. And we know of at least one designer [via UX Evangelist] who is working on the Windows Mobile 7 interface using this very markup language.