that I can customize what I get notifications for. I can silence everything but mentions. So if there's an outage or someone has been waiting for a long while on something they can @ me, but if they just want to have a discussion publicly and let people review it at their leisure, they can do that as well.
Any e-mail client with rules can do that and much, much, much, much more, though. Slack only offers three primitive options for notification filtering, and they can only be applied at two levels.
That's because you're using Slack wrong. You push notifications for a particular topic or event into a Slack channel. You then set notification settings on each of those channels.
Slack isn't the filter, it's the data store and UI.
If you want different types of notifications.. I'd just notify on the urgent stuff and then manually view particular topics at your leisure.
