Dead simple asset packaging.
It's pretty sweet to get really meta and use file-watchers and development flags, and super-fancy command-line programs to do futuristic stuff with your assets before you ship them to the browser. If you're into jumping motorcycles over 10+ school buses I highly recommend.
If you just want something simple where you go "hey, you. Here's a list of files and a key. When I ask for this key, give me all those files concatenated together" then you should use this.
It's dead simple. It's made to be used by something higher level. It's really easy, but I've implemented it 3+ times in other projects which is my "make it a module" litmus test. So...here. :p