The important difference I see in the approach used by backbone is it gets us away from having the server be in control of navigation and UI events. After the initial page load, I'm exchanging simple data as json with the server. It wasn't HTTP I was arguing with, it is having a server side framework managing the UI navigation.

The best way I've heard coffeescript described is as a better syntax for javascript. Though at first this may not seem like a big deal, in my experience it's been a huge deal in the effect it has on how I approach client side code. Now that I can write code I really love on the client, it's greatly lowered the barrier for me to do so.