There certainly are disaster scenarios that can happen. My point is disregarding that in favour of the general user experience. For me knowing that the person at the other side has all of the features I expect them to is great. This goes for support of file transfers or video but also for the fact that all of the buttons are on the same side. (I had to explain over and over where the Skype chat is because the Mac and Windows versions are so different).

If Slack falls then, well, we'll pay the price of migration, but seeing as it is a tool for ephemeral conversations I see it as less of a problem as migrating e.g. my e-mail.