I can't comment on Ember or others, but I think Backbone fits into traditional apps just fine. Where I work we're generally a traditional app with many server-rendered pages, but we have a few parts of the site that needed more complex client-side code and we opted to use Backbone for those.
Backbone is a pretty slender library, you can pretty much use it however makes sense to you. You could go really hardcore and do a site that's client-side-everything, or you could do hybrid approach like we did.
Backbone is a pretty slender library, you can pretty much use it however makes sense to you. You could go really hardcore and do a site that's client-side-everything, or you could do hybrid approach like we did.