Ask HN: Backbone vs no backbone

I want to ask fellow hackers, about the difference that backbone.js makes when it is used as an MVC on client side.

With Backbone.js as MVC there will be a shift of load from server(mostly reduces to an API) to the browser. But HOW MUCH difference does it make, is what i want to know. Will it reduce the load and hence the $$$ on server expenses?

I am comfortable with RoR/django, and have a product in mind. I just wanted to evaluate using Backbone. Is it worth learning Backbone, or going with RoR/django?