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.
Luckily we don't end up actually using this much, but we couldn't live without it.
We use Docker everywhere. Every new service is built in Drone into a Docker image and pushed to our Dockerhub tagged with the git hash. We can then have full confidence we are deploying the exact version of any service.
We're huge fans of Go. We've been porting code into Go for performance and correctness reasons, and most new development is done in Go.