I've been daily driving it for six months now. I wish I would've know the Nix language well enough before jumping in to attempt declarative configurations. Not that it's hard.

I have had issues that have had me temporarily try Pop or Debian, but dependency hell is real and the Nix community is wonderful. I have been able to solve every single one of my handful of problems in less than a day or two (sometimes in minutes) with the community.

Edit: oh yeah, and documentation is not great... Again, the community has been my source of answers to many questions.

As many others have said, it's hard to imagine life without NixOS once you get the hang of it.