It depends if you actually need one. Do you need a full javascript frontend or can you sprinkle JS on top. I'm a huge fan of Backbone. Its small enough to lear

It depends if you actually need one. Do you need a full javascript frontend or can you sprinkle JS on top. I'm a huge fan of Backbone. Its small enough to learn the in's and outs of it and also allows you to control the structure / design of the application. This definitely has pro's and con's but for us it means we can swap developers and theres a design pattern thats easy to understand and implement. We're actually building a pretty large Ember project at the moment (a project management tool called Matterhorn). Its been a great experience and we're planning on using it for all of our client projects going forward. The learning curve is a little high and the 'plugin' eco-system is lacking to say the least. I actually think this is a good thing though as most people write terrible plugins. Roll your own and own it.