It's astonishing how great Slack is at PR. There are dozens [1-12] of competitors with more or less the same product, but only Slack gets all the nice press. I guess they have much better execution too, but all the press surely doesn't hurt.

[1]https://www.cotap.com [2]https://hall.com/ [3]https://www.convo.com/ [4]https://www.flowdock.com/ [5]https://chatgrape.com/ [6]https://glip.com/ [7]http://www.moxtra.com/ [8]http://officechat.com/ [9]https://fleep.io/ [10]http://www.tigertext.com/start/ [11]https://www.pie.co/ [12]https://www.hipchat.com/