I purchased HomePod on day 1 thinking AirPlay 2 and stereo were just around the corner with iOS 11.3 (pretty niave, yes) I will be returning my HomePod today before the 14 day return window expires on Friday. This was the nail in the coffin for me. After also *not* being able to have two HomePods in the same house each with their own iCloud account, the HomePod just isn’t ready for sale yet. Shame, because I love the audio quality and design.
Slightly off topic, but so many iOS features get released and then forgotten. Continuity, universe cut and paste, keychain syncing, beacons etc. Almost everything that relies on iCloud is buggy and unreliable. I expect the same will be true of Messages in iCloud.