What does the company do well? Extremely easy to onboard, you can be up and running in under 5 minutes. Makes it very easy to facilitate communication, and there are SO many integrations that it's almost silly to not use Slack at least in some capacity.
What does the company not do well? I think they could do a better job of providing default locked/privacy even for free users. I work at a university and technically anyone with an email address in that domain can join.
What do you wish you had known about the company before using? That is integrates with so many different other solutions. It may have made me choose a different option for our project management software.