The Sonos One is a great speaker, both for the usual playing of music, but also as a smart speaker to control the selection of music, or asking questions or setting timers, etc. Sound quality is good as you would expect from Sonos.
I own both the Gen 1 and Gen 2 and as it stands now, I can't tell them apart. Sonos says that the Gen 2 has a newer processor and more memory that may enable new functions in the future, so I'd buy a Gen 2 over a Gen 1 (they are still for sale in some places). I don't notice any difference in the sound or microphone performance between the two generations.
The voice control is great. I've mounted one of mine in our bathroom so being able to ask "What's in the news" and have the morning news play while taking the morning shower is handy - or music if you like. It was also nice to see that, after mounting the Sonos One upside down in the bathroom, the Sonos logo still looks the same, since Sonos is a palindrome!
Only 4 stars as the microphone is much less sensitive than the other models I have (3 Sonos One version 1). You have to be within a couple of metres from this Sonos One for Alexa to work well. I don't know if it's this particular unit or version 2 in general.