A few new changes have been spotted after the July 2008 SERP updates that we reported last month.
One forum member at WebmasterWorld thinks that Google might be using different data centers for query refinements. The reason he suspects this is because he's performing the same search but finding different results. It's possible that if Google is realizing that users are not happy with those search results (since they searched again) and are offering a different set of results.
Other forum members wonder why Google's datacenters aren't matched up since they are returning different results.
Another forum member is disturbed because Google apparently rolled back its index. He cites this to "seeing thousands of old 301 HTML pages from back in April from our old site that have not been in the index for 2 months now, right back at the top of the SERPS."
Numerous forum members are annoyed by Google's yoyoing of search results.
Finally, it looks like Google is favoring freshness of results, as one forum member writes:
We're seeing as of today all new content written in July gone from the index, but new content written today appearing in 15-30 minutes after pinging a new sitemap.
Forum discussion continues at WebmasterWorld.