I am on the same page as you. Been conducting the same kind of research by analyzing the first 10 result pages. I think PR is only an enhancement to the search results. I know a few people mentioned this in here before, but you see pages with lower PR come before higher PR for some search phrases.
What I noticed, 9 out of 10 times, the top site has the exact phrase in the search, and a lot of backlinks with the phrase. I have noticed some sites getting tops with the URL. But I am thinking of more the title and the Anchor text. I am strongly starting to go against the PR system. I do not believe in the least bit that it is the premis of the search results, I think it just gives weight, but doesn't actually make you number one for a particular phrase.
Bob Wakfer, who posts in here often presented a well written article in regards to the Algo of google. It is pretty interesting to read:
http://www.compar.com/infopool/artic...lculation.html