Typically, Media Centre applications are written in MCML (Can you guess - Media Centre Markup Language...) but it's good to know that you can in fact use WPF XBAP applications inside Media Centre too.

The Media Centre SDK contains some instuctions on how to do this but for a real example, take a look at this http://www.mobilewares.net/mce/bphtm.htm which is a Flickr photo viewer, written in WPF, hosted as an XBAP and can be used in Media Centre and XBox 360.

That's pretty cool.

I haven't delved too deeply into the exact trade-offs and/or extensions required to really get a 2' and 10' experience from the same core functionality but I'm sure there'll be some extra work. Still, the idea that you can take existing WPF property and move it to 10' is undoubtedly good news.