In the end I had four separate Rails apps in which I had scaffolded exactly the same model, Todo, to provide a backend for different versions of the classic Todos sample app. This led to a great moment during the talk in which after clicking around quite a bit in the client, adding and deleting items, I refreshed the page. To my surprise a completely different app loaded in the browser, the one based on backbone-rails scaffolding. After preloading the page for the talk, I had shut down the original app and started the other. This was proof of how well decoupled the front-end app can be: As long as the server provides the correct RESTful json api (and security features notwithstanding), any server will do! After the initial page load, the server is really decoupled from the presentation layer.
After my presentation, another member of the group followed with a demo of testing a real-life Backbone app, with Jasmine specs that were written in CoffeeScript. It was strong evidence of the positive difference CoffeeScript can make in readability.