You'll get messages on the go – during the honeymoon period, you can even turn on notifications again! – and then need to come back to them later (because you're on the go, and the messages are important).
Then, one of two things happens: either you fall back to email or the IM tool gets CC, BCC, mark unread, search and bulk messaging.
Except that it's shitty email. It's email that's locked inside a social media company's walled garden, with only one client, not federated.