At least on Windows slack has pretty terrible performance. I wish i could go back to hipchat. I regularly experience perceptible lag when typing, which doesn't happen anywhere else.
EDIT: This is a fairly recent problem. A month or two ago, I had never experienced this.
Not recent. May have gotten worse, but last I tried it was heavier than hangouts; yeah, text chat chewing up more cpu than streaming video. Pretty rough.
Folks on Macs had no idea what I was complaining about though. Go fig.
Once you add history to Slack, it's performance is just awful. One of the worst performing apps I use. It can take over a second to switch rooms.
If I have to cycle through 4 rooms to get to the conversation I want, it can take seconds just to Option+UpArrow there.
Plus I can't manually reorder rooms as I like. I don't get why everyone talks about the Slack UX. Slack has snippets. Which I find mostly useless. Especially since they kill performance. But HipChat lets you reorder rooms as you see fit. Which is something I actually used and miss desperately.
At least Slack has finally gotten rid of the useless Channel vs Group distinction?
UX/integrations/apps/speed/etc might all be the answer but it was visceral for me.