This app is very good. (And no, I do not know the author of it at all.) Very well designed and works great for organizing your media.
Media File Manager allows you to organize your media in folders. This is very useful if you are uploading a lot of images at once that are on different topics. Or if you have uploaded a certain topic or type of media over a long period of time. (For instance, I can group all my garden photos that get uploaded over the summer into one folder.) You can also have subfolders. (Tomatoes, Zuchinni, etc. ;>)
When you are ready to put your images into a blog post you can open that folder and not have to hunt and peck through your whole library.
As far as I can tell so far it does not look like you can delete images from within the Media File Manager. It just allows you to group things into folders. It also does not appear to tell you if an image has been used in a post. For those things you have to look in your main media library.
Note: I have only used this plugin with images. I have not used it with audio or video files yet.