Another Google update?

The Google search results appear to be going through another major upheaval. It started about 3 days ago and it seems like many sites are suffering. There is a lot of talk about it over on the Webmaster World forums. Usually changes that seem this drastic and sporadic tend to correct themselves in a week or two - we shall see - someone always seems to lose/win in the end though (for every site that moves up in the results, one has to move down). We have some sites that have been affected and others that are showing no change at all.