Slack is fantastic. We use it at work. All the people that used to use email for all their useless bullshit moved to Slack. I keep it closed and only respond to messages after 30 minutes, which is when Slack sends me an email notification that I’ve missed something. Usually, by then the person has figured out the problem on their own and I don’t have to respond at all.
+1
I’ve also used Teams and other IM solutions, and Slack just feels the sleekest and mostly gets the hell out of the way of what you’re trying to accomplish. I have found Slack voice calls to be a little dicey on desktop sometimes (“hello, can you hear me??”) but always works on mobile.
A client of mine asked me to use it many years ago. So I got on there, and even though I lost that client I still use it to communicate with my team.
Then about 3 years ago I had to use it for a class.
Also have a “day job” with a huge company everyone knows and they transitioned from their own app to Slack last year.
Other use, I used AIM until it closed and most of the people I had on there I transitioned to Slack.
To me it’s just a messaging app.
My co-workers are scattered around the world in a varitey of time zones. So after hours is a rather fluid concept. But I don’t have notifications set on my phone so it’s not really an issue. I’ll check Slack if I’m expecting something.
Give me slack or kill me!
When the newspaper that I work for abolished its copy desk a couple of years ago and shipped all the design work elsewhere, we started using Slack in order to communicate with the remote designers. It’s adequate for the task, I guess. Not that great, though. We attempted to establish a Slack channel for the people at the paper to use for planning budgets and making assignments and whatever else, but even though it did seem like a pretty decent idea, absolutely no one was interested in actually using it, so it more or less withered away.
You may have missed a certain degree of sarcasm in my post 
. I actually don’t have a problem with Slack as an app. I do have a problem with interrupt-based communication, which is a flaw that all IM systems have.
I need to maintain concentration for long periods, which is just incompatible with you-must-respond-in-the-next-30-seconds communication. So I keep Slack closed and treat it as an even slower version of email. When someone does message me, I usually just respond via the email notification, and not in Slack itself.
On rare occasions, I do need some back and forth (say, with IT support), and Slack is fine for that. But it’s not something I keep open willingly.