I'm not sure how to make a "browser.jmd" so I'll just throw a list of suggestions over the transom.
You mentioned new users...
1. Open the Media Library tree one level by default, and leave it open permanently so that the screen always shows "Audio," "Images," and "Video." Eliminate the +/- next to Media Library.
2. Open Playlist tree one level by default (after cleaning it up a bit, hiding the advanced stuff).
3. Allow users to use MC without ever having to open the library trees. The default view when you click on audio (without opening the tree) should be Artist/Album. When users rip their own CDs, these are likely to be the most reliable and usable fields.
4. Replace the text in the top level category labels (e.g. "Audio") with graphics. Bigger, and more visually distinct from their trees below.
5. Allow users to hide groups and view schemes that they don't want to see. They might not want to see all those complex view schemes, but they might not want to permanently delete them either.
6. Include every single useful view scheme that people come up with. Show just a handful in the trees, and hide the rest.
7. Include sample files that will "demonstrate" every default view scheme. It will be confusing for users when many panes just say <all> and <unassigned>. You want them to immediately realize that this is a great tool for organizing all their digital photos.
8. Rename Web Media "Internet Radio." "Web" generally means websites abd HTML.
9. Rename TV Tuner "TV & Video" or just "Video." There are times when an mpg video file is played, but the image isn't showing. You have to click on "TV Tuner" to get it to show the video.
10. Consider a start-up video or audio - maybe a combination of THX and the Apple demos.