It's nice to be able to get off snapshots is the main thing. I don't want a stable version of Leiningen 1.2 depending on some random Clojure snapshot. Plus now the primitives work can get merged to master.
I recommend using 1.2 head. Even if you are learning clojure I'd recommend 1.2 head. With clojure, unlike most other languages, using head is relatively easy, it's stable and faster and it has more features. Pretty much a win from most perspectives.
As soon as put a minimum amount of effort into researching or learning clojure you'll likely switch anyways. I think I switch after about five hours.