The Codeplex page has screen shots and all that, but I have to rave about the simple coolness of it all. Just like in Explorer you can draw a box around the files to pick. Then you can either drag them: onto a folder in the library, to another library in Quick Launch, or to a Parent folder by dragging them up to the breadcrumb. If there's a valid destination on the screen, you can drag 'em there. Now that's cool. It's all done with JQuery, and once you try it you'll wonder how you lived without it. Enjoy!