With Backbone.js, Drupal is no longer a drag when making dynamic, JS-based functionality...in fact, it's kind of awesome. Backbone works by creating lightweight model objects in the browser that are then easily bound to the vast array of interaction events and views using a flexible client-side templating system. Drupal is a great tool for producing the sort of structured JSON data that Backbone consumes: we get the full power of Drupal's Field API and content administration tools on the server side, but don't have to deal (much) with Drupal's theme layer and rendering stack, getting Backbone's lightweight awesomeness in our UI code. It's kind of a marriage made in web development heaven.