I've been using Auction Ads for about three months now and have added them to most of my sites. I even built a site around them to help people find things at Ebay. You can see the site at
www.EbayAuctionAds.com.
They are small text ads that also have images of the auction items. If you have every placed images near text ads you know how effective that can be! They also give you more control over what ads are shown on your site by letting YOU pick the keywords. You can do some testing on my site, the AA site, or even on ebay to see what comes up that matches your site well, and then use those keywords in the ads. They just added a bid range filter option so you can avoid showing ads for expensive cars if you have a toy site, and not show toys if you have a used car site.
The filter also helps to "refine" the keyword results. I was trying to show ads for computer servers, but when I used the word "servers" I got some other things like "cake servers". I put in that the minimum price was $500 and that let me just show what I wanted.
If you want to try them for yourself there are links on the site that will let you do that. If you have any questions, please ask.