I see that Amazon has had PPC product ads available for at least a year. Has anyone tried them, and if so, how were the results? Just to be clear, I'm talking about the ads that drive traffic from Amazon's site to mine...not the associates program or affiliate program or whatever they call it now. I'm talking about the ads that show up with product results in Amazon and say "also available from..." So, anyone used them? How were the results? Any conversions?