Robert_Charlton - 10:03 pm on Mar 29, 2013 (gmt 0)
OK, now I see them. I'd describe the setup slightly differently, in that the Instant Previews are available only for the AdWords ads above the organic results.
When these previews display, all side AdWords ads vanish... ie, the right column isn't partially covered up if the ads extend below the preview. The ads in the right hand column disappear while the preview is displayed. Also, to note again... the AdWords ads to the side get no previews, at least in what I'm seeing.
I'm assuming that the Instant Previews, from the beginning, whether for organic or for ads, were intended to reduce unnecessary clicks. As such, they must have reduced clicks to some organic results, increased them to others, depending on the pages.
Previews on AdWords at the top would arguably have similar click behavior, but the Preview on these would probably make the clicks more likely to convert, thus making them more attractive to advertisers who are at the top. Maximizes satisfaction for top ranked advertisers (ie, as ranked in AdWords). That's my take on it, anyway.
I have no guess to venture at this time whether the new arrangement would affect organic click-throughs more than ads at the top already have.
The cache link, in a small circle that's displayed right in the organic serp, just after the url, is very Bing-like, and an improvement over what Google's had for a while, of hiding the cache link in the Preview.