I started looking into Backbone yesterday and found the initial curve to be so much better. There is no mystery in my mind on how to set up a basic model on top of a resty service and putting views and collections on top. I'm currently trying to decide if I should switch over to Backbone as I learn. I do realize there is a lot more code to write if I go the Backbone route. I think I can live without two-way data binding. However, I think will miss directives.
I first started using Knockout.js and within an evening I was up and running and pretty much knew all I needed to know to get cracking.
Our whole team has been using Angular now for about 2 weeks and we are all still confused as hell about how we are supposed to get certain things working.
I can see the power of Angular, when stuff does click with it, it does really click. I think the problem is that thinking 'Angular' is completely different to working with jQuery and the DOM - for which I have years of habits deeply ingrained in me. The documentation really should make this clear from the start - 'forget everything you knew about front end development and start completely from scratch'.