[jcadam]

My preference is Backbone + Marionette, with Bootstrap for layout. I've tried Angular and Ember and I have to say I'm not a fan.

Take my opinion with a (large) grain of salt. I'm not a "professional" JS/front-end developer. I'm a back-end dev (Java/Scala/Python) by day and really only touch frontend stuff when working on my own projects. My "me" time is precious and I don't want to spend it wrestling with some uber-framework :)

[ralmidani]

It depends on how large your projects are. At some point, the time required to learn an "uber-framework" like Ember is eclipsed by the time needed to implement things not included with a smaller framework like Backbone.