I don't think the parent comment is talking about the UX really. But on the topic of UX and what are or are not losing, I will say that the UX of slack is not

I don't think the parent comment is talking about the UX really. But on the topic of UX and what are or are not losing, I will say that the UX of slack is not so good when it eats 2gb of memory all day and beachballs a modern day iMac quite badly if you have a channel with lots of fancy formatting. I have written to slack about this and they wrote a polite response back acknowledging the issue. Really hope they do solve this soon (Despite the connectivity issues) because it's become unusable for my team lately. Supposedly according to slack it is compounded when you have multiple teams. We have a team per client as we primarily do consulting, so now we have had to switch some teams over to another solution so that we can allow the teams that must be in slack to stay in slack. So, while I think slack has the potential to be much better in every single way, days like today illustrate that it's an SPOF, and on days when it is available, I would not call the experience reliably good, not as reliably good as modern day IRC is, unfortunately. (and I don't say this lightly, i love things like in-line code blocks, @ notifying people, mobile clients, and more)