I do wonder how it will compare to Eclipse Orion's JavaScript content assist which is using Esprima as parser.
http://contraptionsforprogramming.blogspot.nl/2012/02/better...
It compares very favorably. The Orion approach, as I understand it (I only did some quick messing around with scripted, am not an expert) is very local, whereas Tern tries to do whole-program analysis. This should allow it to pick up much more information.
The one exception is requirejs-style dependencies. Those, if you give Tern some information on where to look, it will resolve and automatically include. I'll do something similar for node.js-style require calls in the future.
I suppose you're not doing live type feedback? Given a test suite for the code being edited, that would seem like a natural thing to do.