Has it not taken off? It holds the #5 spot in "Social Networking" in Apple's app store, where it must compete with Facetime. I've been using it to talk to my mother for 4 years. She certainly doesn't care about Google's past messaging blunders; she just likes that it works.

I don't really think Duo would be the best option for Google employees to video chat with each other. They'd use Hangouts, because they all already know each others' G Suite accounts.