The reasons I use these are: 1. Rich content, organized & clean lists with outbound links for status updates about things I'm working on, linking to Asana/Github 2. Notes from one on ones, or general progress updates that I keep in a private channel and save basically as a stream-of-consciousness/reality log, having them there makes them readily accessible in product and having them in Markdown makes them very readable when I'm browsing through.

In short, I treat Slack rooms almost like I would treat a folder in Dropbox, they just happen to also include some chat between people :P