Just imagine what it's like for Amazon, that just rolled out Slack internally last 1-2 months.
(hint: it's not great, but at least we can fallback to Chime)
(hint: it's not great, but at least we can fallback to Chime)
Actual rollout started couple months later. Currently living in a nebulous/purgatory in-between state, most people have both Chime and Slack installed on their laptops/phones. Can't fully commit to just one or the other, yet.