I'm running WatchOS 4.1, and when I ask Siri to play something it works without issue. Of course, some things show up in the Radio app, some come from my Apple Music library. It has been fairly seamless from my usage. I ask for something and siri says "I'll tap you when I'm ready." Another thing that I've noticed on the S3 is that alerts from the Apple Watch finally play audibly in my AirPods, which my S2 had never done.