Rails is nice, at least in the beginning. It's easy to pick it up and build something trivial, but it's pretty hard to solve some non-trivial issues -- you have to learn the framework internals. While, "frontend" side in Rails is pretty easy to grasp, internals are much harder, in my opinion (due to a very large codebase and Ruby's flexibility).

It is definitely a convenient tool, designed with programmer happiness in mind -- so there're a lot of things which will make your life easier. Although, sometimes this UX-centric model backfires and we get such things as RSpec.

Finally, it depends on what you are trying to achieve. If you are into money-side of the question, then maybe JavaScript ecosystem might be more worthwhile. Although, I believe that it is possible to bootstrap demand around tools that you are passionate about if you convince others to think the same way. My point being, that maybe you should look at the technologies that you love instead of following the market hype, but this is more harder and also means more time investment, but it pays off in the future.