If you having a hard time choosing between javascript MVC/MVVM/MVP frameworks (and, let's face it, there's a lot of choice right now!), you might be interested in Addy Osmani's TodoMVC project.
The project implements a simple todo-list application in most of the prominent frameworks that are available, including Backbone, Ember, Knockout and a bunch of others. The project is also on github and accepts pull requests, in case there are frameworks missing that anyone would like to add.
http://addyosmani.github.com/todomvc/
Did you find it useful on deciding, and are you using any particular framework yourself?