tedster - 11:28 pm on Apr 30, 2010 (gmt 0)
People who can accurately spot Caffeine results have already taken some baseline observations in their keyword areas. These observations were usually made last fall, when the Caffeine "sandbox" was available and you could know for sure what was a Caffeine result.
Google tried to launch the Caffeine infrastructure in a way that had minimal impact on ranking positions. Other changes in ranking have been ongoing, but they are due to changes in the algorithm itslef, and not specifically attributable to whether Caffeine is executing the search or whether the previous "Big Daddy" infrastructure is doing the deed.
There have been more reports recently of "rotating results" - even rankings that seem to change with specific hours of the day. It's not clear to me at this point if this is something new that we will live with indefinitely or perhaps just an artifact of nailing down Caffeine for a 100% permanent release.