I should elaborate a little more about the vitriol of my last post.
Google's largest advocates were the more technically inclined. The early adopters and the folks who either made technical decisions or heavily influenced those that did.
This was especially true of Google Talk, which brought the first meaningful interoperable Instant Messaging to the masses, unlike MSN, Yahoo, ICQ, AIM, and several other proprietary networks. This was the driving force to get our organizations to set up XMPP servers, because, hey, it'll interoperate with Google, and we all know Google does the right thing.
Now we're eating our words.
The masses that use Google Talk the same way as they used AIM or Skype or Facebook chat don't care; they were already using the network they started with. Instead, it's the technical folks, and those who listened to us, that are screwed over. Like, oh, our employers.
It was never about "using a single client" -- it was about using a single, universal identifier (not unlike your email address) that let anyone get in touch with you, without having to juggle half a dozen separate logins. With that, clients competed on features, rather than network-effected lock-in.
We consequently built our Instant Messaging systems under the assumption that it would be federated, and now we find ourselves suddenly unable to communicate with an increasing part of our contact lists simply because they clicked "okay" when Google prompted them to "upgrade" to Hangouts. Bang, they're now forced inside Google's walled garden, and all non-google contacts are gone.
If you're going to exist in a walled garden, why not just continue using Facebook? Google is now trying to beat Facebook at its own game, and in doing so, is becoming the very enemy it once decried.