This the question the NY Times is asking in one of its article.
Mike has been reacting on his blog about this:
I’d like to list some devices that are actually shipping with Windows CE (but no one knows or realize it is CE running in there, and this is exactly what CE is about: enabling OEMs to build specialized devices full of features and functionality…)
Mailing machines: http://www.neopostinc.com/
Set top Boxes: http://www.slingmedia.com/
Wireless picture frames: http://www.momentolive.com/default.aspx
Industrial robots real time controllers: http://www.chaveriat.com
There are many other ones and the number is far from decreasing, especially in the actual economy situation where enterprises need to be fast to market and to work on differentiating their products and not on reinventing the wheel or redeveloping an OS. By using and leveraging CE, they get advantage of fully integrated features, still being able to scale the OS to their needs.