imbckagn - 8:54 pm on Aug 24, 2012 (gmt 0)
For what it's worth I am 100% positive there are at least 2 sets of data (search results) being used. I have been tracking this for a while now and it does NOT change multiple times per day. The "second set of data" usually pops up every 2-3 weeks for about 3-7 days.
For me personally when the "second set of data" is being used conversions and traffic quality go up. This shouldn't be confused with the normal churn of the SERP's which happens on a daily basis with the "first set of data".