There are always new developments with directories. When you look at "general" directories, those can be a little "icky" sometimes, but there are lots of directories now that are interactive and have active users much like a forum or blog. And really, a directory is such a loose term.
When it comes to voting, probably only a few sites have come close to mastering it. Digg would be one of those, and probably Yelp would not be one of those. :) That's not to say directories shouldn't try to develop this area! In time, there will probably be some methods that are effective in producing more reliable results.
I've seen some great directories that bring about interaction between service providers and consumers. For example, one really awesome directory provides listings for contractors for an entire state (in the US) and all the contractors drive around with a sign on their vehicle, and thereby increase traffic and leads to each other, so it becomes a great benefit to be involved in the directory.
So integration of maps, and interactivity between users and listers in a directory would be a couple of examples of customizations that enhance user experience.
Concerning surveys, that is a good idea. I personally have thousands I could email in the industry. If you like we could arrange to coordinate an effort to get questions here on Webmaster World that we could then put into a survey, and publish the results. I'm sure it would be good for the industry, and help improve quality and growth.
[edited by: Webwork at 10:37 pm (utc) on May 4, 2010]
[edit reason] Sorry, but no particulars please [/edit]