Slack may regret its letter to Microsoft
It's funny that Slack thinks they've perfectly balanced a unique and special snowflake on the tip of a unicorn's horn when what they've really done is added a pretty UI to IRC.  It's a chat room.  With channels.  So, sorry to tell you guys, but it's not innovative, it's lucky.  We had chat rooms back in 1995.  Yes, that scrappy startup Microsoft will not have too much trouble implementing a chat room and they don't need luck to get users.  How were the people at Slack not thinking "Holy shit, people are paying for this!" the entire time like it was a dream.  I'm sure Slack will continue with much success now that they have their user base, so good for them, but to delude themselves into thinking no one can do it as good as they do is a bit naive.