Awesome 
disko and nixos-anywhere solve some of the bigger painpoints I had with NixOS in the past.
At that same conference, Valentin (fricklerhandwerk) asked if we could make that the default way of installing NixOS? Good question Valentin.
Hum. Interesting thought. Running nix is probably too big of a prerequisite for new users to be the default?
Also, reading the readme again:
Nixos-anywhere does not support wifi networks.
This is surprising, why? Too many user complaints? Difficult to document? Or are chances it will fail on a particularly flaky network, so certain ethernet connections are not supported either?
Wifi is difficult because you would have to export the existing credentials from the source Linux, with all the variants possible, inject it in the kexec kernel, and then again in the target system, with all the variants possible. This adds a lot of variance and testing for a tool whose primary use-case is to take over existing servers.