I use Slack, I have used it for a while now, but at work we don’t use Slack we basically use Skype for business (albeit a little slack). I am probably like most users of company system, where you use really what is installed on the corporate build of the workstation of laptop. I am great advocate of this idea, but I also like free-form collaboration and using tools that are right for the job, which often Skype for Business on its own is not.