Is backbone the best Javascript framework to go with these days? I'm keen to switch to this style of web development but I'm waiting for the community to pick a winner.
I strongly recommend AngularJS. Huge reduction in application code complexity. There are other good frameworks, like Ember, but the only one I wouldn't recommend is backbone. The only things that it has going for it are that it is easier to get started (but harder to continue), and that if you really love to hand roll stuff you get to: both because it doesn't really do that much.
It could be, but it also depends highly on your JavaScripts strengths. With them you could take backbone.js, which is quite lightweight and easy to learn, and create an extended SPA framework that screams.