I'm no expert, but I do have some #UX quibbles. I don't like the four pane concept on desktop. Should be able to make one of the three major panes bigger as you want. I also think they should have taken the next logical step and me this a really easy to use version of IRC....something for the masses unlike Slack.
@designakt Thanks for the reply. Too much is going on. And, really, the eye is drawn to the movement of the fourth frame anyway because of the movement. So, I would make it the most important aspect of the service and hide or lesson the importance of the other three. And, remember, people are coming from the Twitter #UX, so I would take that into consideration.