Ironically, in the FB office we had a separate set of devices (manufactured by Cisco I believe) ALSO called "portals" (they looked like this: https://www.allhdd.com/networking/telephony-equipment/telepr...) that were used to link various parts of remote teams (i.e. if you had half the team in CA and half in NYC, you could set up a persistent video chat between the desk areas of the two. Most teams muted them by default, and if you needed to get the attention of someone on the other side you would wave your arms (or message them) until they unmuted you and you could have an impromptu conversation about whatever it is you needed. While there was some social use from them, they never fully delivered on the promise of "feel you're in the same place" (can't quite shout through the portal "let's get lunch"), and they always seemed better used as "hey I have a quick question that needs to be answered". Some people certainly commented that they found them distracting above all else.
What I find most interesting is that even AFTER sending all employees (FB) portals, FB doesn't seem to be targetting this use case. Instead, they seem to be targetting the "make it easy to dial into a meeting or quickly connect with any coworker" (almost a 21st century equivalent of a desk-phone). I'm curious if sidekick has / will explore a kind of mode for that :) Other than that, seems super cool - a quick feature suggestion is add a light around the camera to give frontal illumination, getting the lighting right for video calls can be a pain.