The excellent sound is above and beyond what you typically get with a speaker with this small footprint. I am not aware of anything that competes at this size....especially in the smart speaker competition.Aside from the excellent sound (which should be a given on a single $350 speaker) I found Siri on the HomePod very impressive. Not in terms of vocabulary or "skills". I just found it extremely natural to interact with the device via voice and the device was lightning-fast to respond.
That said, the lack of a fall-back analog port and some persistent home-kit bugginess killed it for me. I don't mind relying on Apple's technological "magic", but if the magic doesn't work perfectly then a hermetically sealed device like this leaves you with no options other than hoping and praying that Apple will fix their magic.
Eventually.
I don't have any more issues with HomeKit than I have with my Dots. They both run into issues where they can't see the hub for some reason. The Dot also has issues understanding me more often than the HomePod. It will say I have more than one device by X name and I will have to repeat my query. The big advantage to the HomePod for music, besides better SQ, is the fact it can hear me over loud music. I have my Dots hooked up to decent to great systems, but it can't hear me over the music unless I am right next to it, which is a major downside.
In a perfect world, the HomePod would have analog in so I could connect a Dot to it, but with Airplay, it is still open enough to get most everything else I need from it. YMMV