Slack is cool and all, we use it, I know lots of people that use it. It doesn't suck and doesn't make my computer crash. But let's be honest here -- there hasn't been a dramatic shift in communication or how my time is spent for the better. I can set up channels now and put gifs into my chat, which I then promptly disabled because it was annoying as fuck as everyone in the company began doing the same.
Personally I'm getting a bit overwhelmed with all the chats I have to maintain. There's Slack, because its pushed on me by my IT department. There's Skype, which I have for legacy co-worker interaction. There's GChat, which all my friends and family use. There's Facebook, which all my non-friend acquaintances use. In any given day I have 5 windows up, not counting the distractions from SMS and E-mail itself.
Nothing gets replaced...I just have to maintain more. Now I feel like its having the opposite effect. All this communication is actually making me anti-social.