I'm migrating a couple of image-heavy blogs to a new site and this plugin seems to have the exact functionality that I need. Scan the specific site's upload directory and synch the info to the Media Library without having to muck around with PHP/SQL. However, it does not seem to work with multisite enabled.
Does it only look for images in the main /wp-content/uploads/ folder?
WPMS uses a different path: /wp-content/uploads/sites/BLOG-ID/ [new upload path since WP3.5] or /wp-content/blogs.dir/BLOG-ID/ [old upload path]