I work for a company that provides web services for employers and job seekers, so when the Dept of Labor released their API (http://developer.dol.gov/) I quickly wrote a Python wrapper for it. (https://github.com/mattdeboard/python-usdol)

I can say that at first glance the Federal Register API is far ahead of DoL which requires API keys, shared secrets, HMAC SHA1 encryption (for _every request_) and other assorted annoyances that made writing the wrapper a pain (it works quite well and easily however). The API in the OP looks much less annoying.

(edit: I've also got a repo with avery rough Clojure wrapper for the same API. Its very rough as it was a self-teaching exercise but it does work: https://github.com/mattdeboard/clj-usdol)