The ads are indeed from AdWords advertisers, but that's about the only thing in common with the AdWords engine. "Search Sponsored Links" does not rank ads in the same way and it does not use the advertisers' keywords as triggers to display the ads. They made those changes back in May, and I wrote about it briefly over here [webmasterworld.com] (June 20 post).
The change to display the ads in a grid was more recent than that. But I'm still puzzled about the purpose of the new "Sponsored Links Search"... Are there really a lot of people that want to search based on the content of ads rather than the keywords for which they are displayed?