If you included guitar tabs and perhaps allowed users to upload custom tabs (so that people can improve on publicly available ones), it'd be absolutely great. I'd use it on a weekly basis at least, if not daily.
A better use of your time would be to cultivate your collection of videos. I think a collection of searchable video tutorials on how to play songs is a neat idea that addresses a different need.
I'd love to visit one that has a clean design with correct tabs and videos without all of the cruft. This site seems like a great idea if you can manage to load it with plenty of content without running into legal issues (I've seen many tab sites get shut down).