[zymhan]

> Is it well-supported enough to use day-to-day as a developer?

Speaking as someone who knows the developer: no.

> Do you often have to build things from source?

There's ~6500 packages, so it's likely you'll be installing some stuff from source. It's really hard to predict without knowing specifics though. http://hydra.nixos.org/eval/1237359

[mjhoy]

If you track 'unstable' you generally don't need to build from source as that branch (or channel as Nix calls it) is updated only after everything has been successfully built on Hydra. There are sets of packages excluded from the build but I think those are mostly interpreted languages (emacs packages, etc).