I joined the Beta yesterday and so far so good. Everything seems to work well and I'm excited for the full release. two things are needed, allow Alexa to access the local music library (NAS Drive ) and also Spotify to stream to Sonos.
Quite by accident I discovered the following feature which I think is awesome.
Using the Amazon Shopping app you can control Alexa from your iPhone, just hit the Mic icon and speak.
"Alexa Play songs by Billy Joel on the Patio"
Can be a bit hit and miss sometimes, but does work.