Several months back Google begain testing AJAX search results. While it has not been rolled out to the general public (and there is no word on when that might happen) it does signal a pretty significant change is fast approaching - especially since they've solved a major reporting/tracking issue.
The problem with AJAX search results previously was that Google was not able to pass referrer strings to the receiving sites. The result was that SEOs didn't know which search result placements were generating traffic. Fortunately, Google was aware of the issue and has pretty much solved the problem.
Within the new AJAX search results, Google's referral string changes from "http://google.com/search?q=" to "http://google.com/url" and will have the query embedded in it. Plus, the referral string will also have a parameter that indicates the actual position where the click originated. This might not be a feature that is around forever, but it is useful to compute ROI without having to do a lot of work.
Have you seen the Google Ajax results? How about in your analytics? Any change? Let us know by commenting below.