I really enjoyed the results of NixOS with flakes but a couple of things were a little more challenging than I have time for to switch it into my daily driver.

It was that steep curve that stopped me going back to date; I liked everything about it, the community was very welcoming and helpful, the declarative nature, and ability to define my machines' states in Git, the documentation, no complaints except the time I'd need to feel as proficient as I am elsewhere.