We'll be taking this for a spin. I've been pushing for an API-driven site for awhile but the case for that model was cinched when we started adding non-web clients to our system.

A leaned-out Rails is a nice compliment to other bolt-on API options and fat GUI-based API builders. Personally I prefer to start with something even simpler, but the facts are you can cover more ground faster (and potentially safer) with something like this vs. building your HTTP stack from scratch.

The Hypermedia stuff is most exciting to me, as hand-rolling that is a hard-sell for many teams (if you have a system of any significant richness).