Yes... Yahoo Directory is one of only two places that Google's Webmaster Guidelines specifically recommends:
http://www.google.com/support/webmas...n&answer=35769
"Submit your site to relevant directories such as the Open Directory Project and Yahoo!, as well as to other industry-specific expert sites."
I've never seen a site get rejected, but I've only submitted quality sites. (e.g., Don't submit a scraper site or a parked domain.)
You don't need to add yourself to the Yahoo Directory to get high rankings, but I think that it is worth the $300.