Missing multi-speaker functionality
This is all very good but I've been able to do audio notifications (such as TTS) to my Bose speakers via Home Assistant for a long time (without an artificial API limit imposed). So what exactly does this add? The ability for it to gracefully resume what it was doing before the notification is something I suppose, but again that would be possible using the existing API and Home Assistant in about 10 minutes, to preserve pervious state and resume.
My biggest issue is it doesn't support groups of speakers and is quite slow to start up (4 seconds). So for me, in terms of household notifications it's quite a poor experience. Just my feedback.