The HomePod is a good option if you care most about audio quality and you use Apple products. It's not as versatile or as smart as the Amazon Echo or Google Home product families, largely because Siri isn't as advanced as Amazon Alexa or Google Assistant. But it beats those products if you care about two things: privacy and sound quality.
Apple HomePod Pros:
Apple says almost all of the processing is done on the device itself, so your conversations are not stored in the cloud as they are with Google Home and Amazon Alexa. Also, I've found that the HomePod sounds better than any Google Home or Amazon Echo product; it gets nice and loud without losing a lot of quality.
On the other hand, at $349 it's more expensive than other speakers, like the Sonos Play:1, which I think is really close in quality.
Apple HomePod Cons:
You can control smart home gadgets that support Apple HomeKit, including outlets, door locks, garage door openers, lights and blinds, but there isn't as wide of a selection as Amazon's and Google's speakers.
Also, while you can ask Siri to play music, it will only listen to your commands if you subscribe to Apple Music. If you want to play Spotify or another service, you need to use AirPlay to play the songs from an iPad or iPhone. Also, while you can ask Siri to take notes, add reminders and more, it only supports one user at a time. In all, you can count HomePod's skills on your hands, while Google and Alexa have hundreds of skills.
Finally, it's expensive. You need one for each room if you want multiroom audio, and Apple doesn't sell a $30 version as Amazon and Google do.
Variations of the Apple HomePod:
Apple HomePod $349