I do use google analytics or (more commonly) web server statistics to track precisely where my traffic comes from. These statistics form the basis for my statement that Yahoo directory listing doesn't seem to give me much traffic.
Specifically, when I try Yahoo with a site that hasn't previously had a Yahoo directory listing, I see only the slightest bump in traffic from Yahoo. Therefore, my conclusion:
COST OF YAHOO DIRECTORY/ PROBABLE EXTRA TRAFFIC = HARDLY WORTH IT
BTW, I'm not surprised that the Yahoo directory doesn't generate traffic... I am--and maybe this is naive--sort of surprised that a Yahoo directory listing doesn't indirectly improve rankings by Yahoo search engine. I remember people speculating years ago that a Yahoo directory listing might improve Google organic search results ranking.
BTW, sort of a related point, since it's Saturday night and Elton John said it's alright to (start) a fight. I have used Google conversion tracking to check how well Adwords convert. Because I sell a downloadable product and can place the conversion tracking script on the page that someone must get to to download the product, I really, really, really should know when an Adword converts. I have found that economics of Adwords often don't work for some products.
NOTE: I do think they work for other products I sell. E.g., for my CPA firm. And yes I know how to do PPC. (I had a friend and Google genius help set it up for me and have years and years of PPC experience at this point.)