For varying values of "just fine". For me, hangouts is probably the worst performing app on mobile, desktop and tablet. It's so bad that even Skype shames it. And FaceTime...well let's not even compare.
But aside from that it has generally been way more reliable for me too.
Think on that for a moment - "Sorry grandmama, I can't send you iMessage or talk to you in person since you didn't spend your pension on an expensive Apple device."
For something as fundamental as human-to-human communication, closed, single vendor, protocols and systems deserve every criticism (and yes, Google deserves it as well).
No one ever claimed FaceTime works on your android. They wanted to open source it and got fucked on patents.
Try using gmail to send a regular iCalendar format invite to an event. If they just happen to have used that email for a google account, fuck you it ends up in the Google calendar account they likely didn't know they even had, and never goes to their email.
THAT is unexpected, and arguably deceptive behaviour.
Correct me if I'm wrong but I've read that they actively shutdown or circumvent projects to create other clients. If they really didn't consider it a strategic asset to push people to iOS I doubt they'd bother with that.
Facetime is just a feature. It's a calling option in contacts and any phone call to another iPhone can be turned into a facetime call at the push of a button. That means you don't even need to think about it. There's no install process, no configuration, no account to set up, it's just there.
Furthermore because it can rely on guaranteed hardware features it has the best compression, bandwidth utilization and image quality in the business. If it's a joke, I'm not sure who it is that's doing the laughing.
It works for calling people who bought from the same brand as you, it doesn't work for the rest of people, and it pretends to work (WTF?) for people who used to have the same brand as you.
That's a very different bar from just needing to install an application.