MSE is actually really cool and makes streaming media over HTTP much more pleasant. I'm not surprised they want to keep the number of codepaths they have to support low. As the GP mentioned, MSE is coming to Firefox soon anyway.

Hardly. The "new code/technology" is completely open spec/proposal and its implementation is open source in Chromium. In terms of "Google pushing it", the spec was co-edited by people from Microsoft and Netflix. In terms of "supported only by Chrome", this is strictly Mozilla's fault as there is nothing stopping them from implementing the spec today.

This article and a lot of comments here are really sensationalizing reality. Google needs to serve tons of video data efficiently so they are motivated to push things like MSE. Reading this as "Google crippling Firefox" seems really dramatic and contrived.