but the API
I'd beel a little more sympathy for Slack if they were a little more open on THEIR end. Quite simply, the UI for Slack is shit. For IRC (and Sametime, back when I had occasion to use that) I could have it write the channel traffic to log files. If I needed to look up old information, a simple Grep would often find what I needed.
Slack? No, sorry, you need to use our crap search that really can't find anything. Scrolling back? Yeah, maybe a day or two, then it ****SLOWLY**** has to retrieve one more day's logs at a time. If you didn't paste some useful tidbit right then, it's lost forever.
They ONCE had an API so you could have maybe had the chance to make a better front-end, but they killed that one right off. You can make add-ins, but you have to run them WITHIN their crap interface.
And let's not forget the abomination known as "Threads". Makes it impossible to follow the flow of a discussion when it makes you open a buttload of sub-threads which you cave to move back & forth between, losing the full flow. Properly there should be a way to flatten those threads, but Slack thinks you shouldn't be allowed to make it work with your own workflow.
And the notification sounds? You can't add your own custom ones, which means that since their built-in ones are nearly inaudible, if you have bad hearing you can never hear them.