Why not upgrade to Lodash?
Given that we're trying to move away from jquery more definitively, I think we'll probably begin to rely on our js utility library of choice a bit more. I find myself reaching for it more, anyway.
Lodash is, more or less, a superset of Underscore.
From the creator of lodash:
I created Lo-Dash to provide more consistent cross-environment iteration support for arrays, strings, objects, and arguments objects1. It has since become a superset of Underscore, providing more consistent API behavior, more features (like AMD support, deep clone, and deep merge), more thorough documentation and unit tests (tests which run in Node, Ringo, Rhino, Narwhal, PhantomJS, and browsers), better overall performance and optimizations for large arrays/object iteration, and more flexibility with custom builds and template pre-compilation utilities.
Because Lo-Dash is updated more frequently than Underscore, a lodash underscore build is provided to ensure compatibility with the latest stable version of Underscore.
Here's another article highlighting some of the differences between lodash and underscore.
Migrating would be fairly straightforward
I assume underscore was thought to go hand in hand with coffeescript, which we've also moved away from.
What do you think?