I've gotten over all the features of Nix, its become my environment of choice. What continuously impresses me now is the Nix community. An issue with your system can be resolved within minutes of a github issue submission. I'd like to see them use the ZeroMQ C4 development contract (http://rfc.zeromq.org/spec:16). No branches everywhere and it's just a rolling release. I highly recommend this distro, it has given me trouble in the growing stages but it's maturing nicely and things are starting to just work.