HomePod Mini is primarily a speaker you can AirPlay to which happens to have some basic voice control functionality. I'd really love them to be a bit more usable (in particular I want to be able to change the app it sends reminders to) but my experience has been that they're fine for music, timers, and basic smart home control.
I guess my age is showing, but isn't it just a mono speaker? so much is lost in music without stereo imaging. it's one of the main eyebrow raising things to me about most bluetooth portable speakers. If you're mainly listening to podcasts or playing lullabyes to a kids room, sure, but we're adults here and personally I like listening to stereo way to much for these to be an option.
Definitely showing how deep down the Apple rabbit hole I am but I have a pair of them connected to my Apple TV which are the ones I use for music/TV/games. The single one in the kitchen really only gets used for podcasts and audio from the iPad I have for watching YouTube and trashy TV while cooking.
Yup, its about as slick as you could ask for. They appear as a single device to anything connecting and then distribute the left/right channels between each other. I've also got the Apple TV set to use them as its default set of speakers, and that handles ARC over HDMI from the TV to send audio from anything else plugged in to them.