Backbone.js is easily one of the finest products I have had the pleasure of using. There is a small learning curve but after that, it's butter. The best part, imo, is that more than teaching you to use some foreign dsl, using backbone.js makes you just better as pojs because it teaches modularity, sane callbacks, and a whole mess of other stuff. jashkenas and the other guys behind backbone did a really good job at making a tool that felt like native javascript.