You looked at YEP? The same developers made TagIt. YEP has TagIt on steroids as part of a much more sophisticated document management program created for people who like their files organized visually. This is one manual you have to read, however.
http://www.ironicsoftware.com/

It works across drives, and newly mounted volumes.

Batch tagging if you forgot to do it, or if the docs are 20 years old. Collections. A magnifying glass that lets you peruse portions of docs on a storyboard-like viewer that shows scaleable thumbnails of your docs.

Some intro videos to see how it works.
http://www.ironicsoftware.com/yep/video.html