Plus in the organic search i find you get no traffic. Im a google man myself.
Another thing is i have spoke to yahoo a few times and they have said they are bigger than google this did make me laugh (but i might be wrong) i think this was their sales pitch.
I do think if you work on google you cannot go wrong as the other search engines will follow.
Personally i think PPC just runs a bill up as you get competition clicking on your ads and people just browsing the internet with no intension of paying for a service or product.
I have found facebook a very good site to get sales here is my facebook group here
www.facebook.com/home.php#/group.php?gid=63985577223&ref=ts
Another thing is to offer something free on your site then build an email list and send them a newsletter once every month.
Hope this helps