I never really got media library part... I am writing my posts in Windows Live Writer from day one and it was just natural to drag and drop image there and have it neatly uploaded to separate directory per post.

When I hit some limitations of hand code approach I just added some custom code snippets that do two things for me:
1. insert often used images from special folder with shortcode.
2. scan post for image of specific size.

It isn't really duplicate of media library functionality but it covers my needs for now, so why bother with more.