Its worth it to be listed in Yahoo, you do get some quality traffic your way from Yahoo directory listings and its a strong directory as well, so affects Search Engine Rankings and the Yahoo Directory does pass PR.. so. IT
Yahoo! Directory Listings and Google The Final Word on the Yahoo! Directory And Yahoo Directory now uses direct static links for the listings.
Based on experience Yahoo directory will give you a solid backlinks. Just recently we got listed on PR7 page of Yahoo directory and our rankings in SERP went up a bit. It's really worth it IMO.