I used it a lot, not through Google’s gchat stuff, I ran my own XMPP server. It worked really well, I used the OTR encryption plugin in pidgeon. My work also used to use xmpp for internal chat within the company, however they switched to matrix like 5-6 years ago. Something I’ve since done personally too.
I like XMPP a lot, it worked well, including it being federated.