I also have Alexa in another room of the house. It serves two purposes, turning on a lamp and turning on and off Harmony activities. With all the compatibility issues and little standardization and knowing Apple was very strict with who is allowed to touch HomeKit, I decided to setup Homebridge. Siri is now able to do a lot more now. Apple also lowered their gates a little by allowing software encryption instead of requiring hardware encryption. I think there’s a lot more to this HomePod than initially meets the eye. It’s a Smart Home Hub too. And when you combine a great speaker, good source Apple Music, Siri, and automatic integration into your already existing Apple Ecosystem, which is so deeply embedded in many peoples lives. Alexa isn’t that close to her users, she’s a little shy. Whereas Siri wants to know what you want to tell her. Siri on everything else, so I have no reason to think it would be any different on this speaker other than some commands being disabled.
Alexa should be able to do everything the Homepod can do, beside play Apple music via voice command/natively (again, Sonos airplay 2 gets around this a bit), and send actual imessages.
Alexa can control nearly ever smart home device/system out there. Alexa can't do homekit, but she can control anything homekit can control, just as well as siri (if not better, siri voice recongition isn't great...I run into problems with it on my iphone and apple tv). So the only advantage here for the homepod is homekit itself, which is just a system for smart devices. I control my nest, lights, etc with Alexa and Google Assitant.
Apple Music isn't a superier service, comparitevely, to Amazon Music/Google Play Muisc, Spotify, Deezer, Tidal, etc. It is a personal preference thing. Tidal is obvouslly the best for pure quality, while I would argue Spotify has the best curation. Google has youtube red/muisc included, and Amazon Music is actually pretty nice (trying it out currently). I use Apple Music because I like to run with just my Apple watch. I also have Google Play music (for the wife) and Amazon Music on trial right now. Honestly, if I had to pick one, it would be a close call between Amazon Music and Google Play Music, with Google Play inclusion of Youtube possibly swinging the score.
I type all this to say, the Homepod is going to be a great sounding device in a sea of smart speakers. It might be the best sounding one with smart features, followed closley by the overpriced Google Max, and the $175-200 Sonos One...which when paired in Stereo mode will offer the best sound.
But the Sonos One works with Alexa, Google Assitant (soon), and Siri/Airplay 2 (soon) via apple devices. But, what swung the argument more so, was that Sonos is a system. Want to add a bigger/smaller smart/non-smart speaker to you house? Great, a new Sonos device will incorporate into your already set up system. Home theater to smart speakers.
I don't have a loyalty to any company. So I don't know if I will be in the Apple eco-system as much as I am now, two years from now. So Sonos is the safe bet.
That being said, I am looking forward to reviews on the devices actual sound.