[jfaucett]

As a js developer, I'd say node of course. But it is true that its backend usage isn't exactly exploding. Personally, I think this has more to do with the types of guarantees (or lack thereof) that node gives you on the backend. I see a lot of rails and jvm language backends for building services these days. You might want to consider familiarizing yourself with the jvm and picking up clojure or scala.

I tested out go for a couple months and found it to be a very interesting language , but I still wouldn't build a rest api with it unless that api was very simple. Its a great language for many things, but I can't imagine a lot of people are using it to build larger mvc service based applications and don't see this happening for the foreseeable future.