If we are not spamming there and if most of our answers are selected as best, you may get better traffic
If your website or the question is of interest then only you will get good amount of traffic and that too on a long term. But it needs to be on top as Best answer. Or else ask a question yourself about the site.
as for Yahoo answers, as a service company I do get alot of turnaround. The only issue is that I am selling to a local market! If you are looking for a broad market Yahoo answers is a good place to advertise! www.jimmycashplumbing.com
not much, if it rank well for a competitive keyword it has a high possibility to get traffic but its not huge as expecting... because they need to see your link first and the direct link goes to yahoo answer so I think its not that successful.
Yahoo Answers has worked pretty well for me. I'm getting quite a few referrals from the links I have placed. You just have to make sure to answer questions directly related to your field so when users click the link, they see what they are expecting. Also, be sure not to spam the site with your links because people will notice which will give your site a bad rep and you may get banned.