It's getting long in the tooth by Google standards I suppose. Who knows when they'll axe it.

I think it's strictly 1:1 (which, I gather, Facetime isn't?). It has good video quality, but what I like most about it is that it's nicely resilient on dodgy connections.

I've often used it wandering around my garden, at the fringe of Wifi range, and it does the right thing: tries to stay on Wifi, but switches over to 4G if the connection becomes too dodgy, then back to Wifi once that's stable again. All of that with pretty minimal artefacts.