We use it at our small (15 person) startup. I like that topics are light weight, like git branches, but despite that we struggle to use them effectively (generally dumping thoughts in a select few topics)
One major quirk of the interface is that can be difficult to, at a glance, identify what topic/dm you are actively on, which has lead to a handful of "Oops, what was supposed to be a DM" message deletes.
We’ve struggled with that in the past as well, but it got better over time. One thing that helps is to aggressively start moving messages to new topics once things go beyond a few in a general topic.
One major quirk of the interface is that can be difficult to, at a glance, identify what topic/dm you are actively on, which has lead to a handful of "Oops, what was supposed to be a DM" message deletes.