Re: MSFT has experience
recently started a new contract, and they use slack. so I did it on an android device (follow invite link, install app), and it has its use but I need shared files on a desktop machine [not on a slab] and so it made more sense to use github to share files [that and set up a source repository].
Maybe if it were more like IRC, and less 1:1 personal messaging... then again I haven't used it enough to understand all of the features (yet).