Inspired by ThoughtWorks, this is our technology radar for JavaScript-related technologies.
We use JavaScript client-side, and for processing some server-side assets. We don't use any JavaScript server-side frameworks, though. While we understand the potential for sharing code between the client and server, none of the server-side frameworks are compelling. Plus, it's sometimes good to make a distinction between the 2 sides.
We also use JavaScript for most of our mobile applications. We find that the Cordova (PhoneGap) framework provides an experience close enough to native apps, while spending significantly less time and money. We're also able to leverage our HTML/JavaScript/CSS knowledge and tools.
We've used a few client-side frameworks (Backbone and Spine most extensively). But we're not really happy with any that we've used. Ember and Angular seem to have the most momentum – we'll likely look at them next.
We've not tried any of these yet, but we're looking into them.