Man, as much as I love Cog, I've been waiting for this as all of my music is on an external disk which I connect my laptop to.
Because I have 20000+ songs, I have to wait half an hour before I can search all my music... really annoying. Especially because I'm a last.fm user and it won't scrobble without the info loaded...
By the way, isn't the tag info saved in a M3U playlist? Isn't there a way to save/load that?