This sounds like a total nightmare. I am very interested in Nix and was strongly considering setting it up on my new travel laptop as a daily driver but stories like these give me pause. I would love to get a more detailed explanation of what happened here. Either way I am past the phase where I'm comfortable or patient enough to beta test software so Debian / Ubuntu it is for me.

Also Nix first tries to find a derivation in a remote cache and sets a very long timeout, so when you have a limited connection (e. g. a corporate limited network setup), it's painful.