We switched from Slack to Hipchat and have been very happy - we no longer have issues when connecting and disconnecting from our VPN, and robust editing of previous messages is a useful feature.
I first heard about Slack from my friend Matt (shout out to Final!). He was helping me out with some Rails issues so we started using Slack and I liked it. Specifically, the chat interaction. But also all the integrations. I wasn’t thinking of it as a tool to end all tools at first, just a chat tool with some cool integrations. Then I created a Slack account for StackShare, and that’s when things got real.
Sentry got easier to stay on top of, Heroku was easier to see activity from, discussions were more fluid, and the mobile app was killer. Most of the tools I use either don’t have a mobile app or have shitty ones. Slack is like a replacement for all the mobile apps my tools should have.
I don’t find Slack particularly useful for focused discussions, so I doubt it will replace email anytime soon for us. Things like product discussions/debates are best via email. It forces you to think before you type and have a clear back and forth with someone.
Small gripe: I wish Slack would disable email notifications by default, I still haven’t figured out how to turn those off.
Our team is partly distributed, but we would still use Slack even if it weren't. Keeping conversations asynchronous ensures nobody will be kicked out of "flow" during their most productive hours.