Around about ver.260, several of us were having trouble getting our media keyboards to work with MC11, while they were working just fine with MC10. Media keyboards have added buttons for volume, next track, etc. There are two major types, MSFT and Logitech, and under MC11, you couldn't get both to work at the same time.
This apparenlty is due to the way MC11 talks to keyboards, I guess. jriver went through about 20 versions dealing with this issue, which JimH termed a "moving target". Finally, he got it to work for everyone, but just in case it stops working in the future, the media keyboard settings allow you to toggle between the various levels of communication between keyboard and OS: either keyboard driver, OS default, MC commands, or give up completely. Until we got the buttons, a lot of us had given up completely.
So a big thanks to JimH and jriver.