I hate it. Just a few minutes ago I saw my site ranking #2 for a keyword & when I logged out it was back down to the second page. The way this is supposed to work, sites that you visited previously will be ranked higher than other sites.
I suspect there is a certain random factor involved Google search results. I have noticed on many occasions that using the same terms to generate new search results within a relatively short time span yields different results. It may be that the search engine ir programmed to presume the results were not quite right, even though you may have clicked on a link. This does not alway seem to occur. Therefore it may be a reflection of the number of "quality" results for given search term(s). In other words, if there are 20 sites with the same ranking for the same search term(s), Google may mix them up to give each an equal chance at page one. It would not be fair to never randomize order for sites with the same ranking for the search terms. I am trying to distinguish between overall site ranking. Perhaps a PR1 website would display higher for a given search term than a PR5 site because its target page actually ranks higher for that specific search than the page which contains those terms on the PR5 site.
A lot of people don't log out after using gmail & they're all seeing personalized search results without knowing it. Sucks.