Conversations involving multiple participants, allowing collaboration and information sharing in Teams
It took me all of 20 seconds to revert from "Try the new Teams" because this non-sensical change modified the usability and meaning of every conversation that I've been pushing to happen in Teams channel instead of the completely useless noisy group chat and meeting chats.
Just now, it looks like this behavior has become standard for me, even with the "Try the new Teams" button disabled. I don't actually know how I'm going to work tomorrow - and if asked why my productivity and communications suddenly plummeted - this post will be my answer.