Make it feel more like slack.
The layout of slack just makes more sense. The feed is just confusing and useless. The chats are completely disorganized. I like the list on the left of slack with older chats filterered out. Channels is confusing to figure out. And user permissions are just ridiculous. Why not give permissions by channel. Maybe these are a bit of "I'm a slack junkie", but if you're going to take over the messaging world, make it similar to the best product on the market right now.