There have been scattered reports of a page rank update. I see no evidence as of today (Sept 14). I have about 40 domains and there was no change in page rank of the dozen or so I watch. I am skeptical about these reports.
There is possibly an update coming at the end of September or even early October. I am interested in seeing how my Harmonica Tab site changes after my rewrite. It gets the most hits of all of my Blues Harp sites, but pays the least.
I did a complete html rewrite of most of HarpTab.com. I tried to use SEO principles as much as I could. Adsense payouts per click have increased, and I am hoping this is because of the better written HTML and the attention I paid to keywords in the description META, the TITLE tag, and H tags in the content. In total there are changes to about 10,000 pages (most of which are generated by PHP from a database). I fixed up my htaccess to make use of meaningful canonical urls and I submitted xml sitemaps of all the level 1 and 2 pages in the hierarchy to Google, Yahoo, Bing and Ask.