I've tried it yesterday. It works well, a little too well in fact... I installed the package, loaded my usual library, and made a few clicks on the playing now libraries and on some random songs in a pane, just to test how MC's multi-zones worked. AC/DC started to play in my living room at 1AM at a quite high volume. Forgot to turn the amp off...
So the good point is that it works well, without any effort. But regarding MC's ergonomy, something is not very clear. Could you please do something to indicate in which zone a song will play when you just double click it ? It seems that MC uses the last zone "activated" (the last one clicked under Playing Now). Maybe update the "Play" menu item to "Play in that zone", or change the icon of the UI active zone in the Playing Now tree... My neighbors would appreciate ^^
Anyway, this integration is really nice, thanks!