I know about the s// substitution, but it just isn't very useful. Sometimes I'll have sent a couple messages before I notice a typo. Also, it's very limited in the type of edits it can make. Last time I tried to use it I realized I had typed "it's" instead of "its", but it turns out I had already using "it's" earlier in the message. I ended up making both "it's" wrong instead of correcting the one I wanted to.

Slack added @here a few weeks ago. Otherwise that would have been on my list of Hipchat pluses.

Being able to rearrange channels would be nice, but it isn't a big deal to me. I mostly use the "Jump to next unread message" hotkey in Slack to switch between channels.