I have a 2 sites that are doing very well in Yahoo now as well; sites NOT listed in Yahoo's Directory. The site that I work for (my real job, lol) has a Directory Listing and it sucks on some terms we need in Yahoo. The Directory listing is actually hurting us in Yahoo's own search results. We contacted them to change this and, of course, they never answer. Yahoo should NOT use the Directory listing in the search results.
I would NEVER submit my own sites to Yahoo's paid directory because of this. I am actually liking the rest of the results though.
I'm questioning the Yahoo listings as well. It's messed up our meta title text with the directory title put in by an editor - resulting in less obvious listings.