The last point the op makes is that you don't need a nodejs framework if you're using backbone/angular/ember. I've consistently used Socketstream combined with Ember in my for-fun projects, and it's extremely easy to build use. Combine that with the massive fun I'm having pushing events to the client from node and watching ember observers adjust accordingly, wonderful things can happen.
On topic - Socketstream is actively being developed and is pretty damn awesome (not to mention easy to pick up). Meteor and TowerJS turned me away when I saw the amount of rigidity in their implementations, whereas SS allows you to plug modules in and out of the framework with ease.