We're heavily Slack-addicted here, and use the integration extensively. Also helpful if you have use-cases for regularly needing to give people access to other objects, the user can click 'Grant Access' directly within the Slack app without logging into WF. Similarly useful if you use the approval workflows or issues, easy access to your to-do list.
We do find it occasionally disconnects, though haven't tracked that back to where the issue is actually coming from.