I find it a bit ironic that a script which purpose is to decrease loading time throws in the kitchen sink along with it. The other stuff (i.e., CSS, screen size detection, etc.) would be better suited as a separate library, imo. There's also LABjs, yepnope (which is a wrapper around LABjs) and RequireJS (which includes a module system, and is available as a jQuery plugin). If you actually just wanted feature detection, there's Modernizer as well.
Edit: ah, apparently the loader can be used standalone now in the latest version, though there are still a number of issues.