I dont. Its honestly not great. I’d rather that effort went to preserving and repairing the existing tools of the free and open web – the old protocols are extensible. Imagine if we had an RSS client with a “reblog” feature!
“Federation” adds overhead and honestly creates as many problems as it solves. It’s not a selling point, its a price tag.
If they enable IMAP for all accounts that’d be awesome. I’ve been reluctant to use their mail system in case it just becomes another lock-in.