In my opinion, the build process of a JavaScript application should be a separate thing from the libraries you choose to make it with.

That said, we (DocumentCloud) have also open-sourced Jammit -- the library we use to build JS, CSS, and JS templates into asset packages for production:

http://documentcloud.github.com/jammit/

Here's a screenshot of what it looks like to have a bunch of Backbone Models and Views that will get Jammit'd into a single file at deploy time:

http://cl.ly/803f3e67692572d76abb