This is a file manager, but it acts as a Media Library. See how it can show the music’s metadata in the columns. You can edit all of the metadata, even in batch.
Here you can find a few examples of its features. Skip the sorting and look at the grouping, custom metadata filtering, etc. not to mention the advanced search with any of this metadata.
Custom File Properties aren't new in Vista - they date back to the Windows 95 Shell API. The only thing Vista added was the ability to filter and group directly from the list-view column headers (in Windows XP you could group-by, but with limited options, and no in-place filtering).
I think XP's File Explorer was the best. Keyboard shortcuts that actually do things useful: keypad * will expand all directories under the current one if you select the item in the tree on the left. A great way to make your hard-disk using friends sit for a while - select C:\ and press * on the numeric keypad...
Please elaborate.