I ran sid in serious production when I was younger and more foolish. The trick with unstable distributions is to test before you deploy and know the incompatibilities and have the fixes ready in advance. The problem is you are basically taking a snapshot approach and doing the work of the debian release system yourself and doing it half-arsed. An urgent security update comes out and you can’t rush to deploy it without risking a dependency being pulled in that breaks under your config. For servers it ends up being a huge amount of work for no gain and you can actually miss out on security updates.

BTW this approach is why Valve can release Steam OS based on Arch or Google can base ChromeOS on Gentoo and release them to millions of consumers safely. They freeze updates to create a release candidate and test it and they deploy a limited subset of packages.

At home I update one arch desktop machine to work out what breaks, how to fix it and seed the package cache on our server before I do the rest and break everyone’s systems. I could do the same with Sid but Arch, despite being unstable intentionally isn’t all that unreliable compared with Sid though my experience with Sid is dated.