I daily drive NixOS. I don't have a global "userland". Packages are shipped from upstream and pull in the dependencies they need to function.
That means unlike Gentoo, I've never dealt with a "slot conflict" where two packages want conflicting dependencies. And unlike Ubuntu, I have new versions of everything.
Pick 2: share dependencies, be on the bleeding edge, or waste your time resolving conflicts.
Yeah nix is great for this. Also I can update infrequently and still package anything I want bleeding edge without any big issues other then maybe some build from sourcing.