Where is Audio 5.1 or 7.1 support? Google assumed that all have stereo speakers at home.
First update is useful, at least it's offer high quality music, but the second upgrade is usually a gimmicks to sell more units of chromecast!
I have the 1 gen Chromecast Dongle, able to cast Audio using app from Play store -Cloud Player! No need to have a separate dongle for Audio!