Matt Cutts says Quality Equation or a Hardware update on the Google Search Algorithms, the testing happens on a single Datacenter first and then implemented on the other DCs.
Answer to the actual question asked as "should all things on same Class C IP block are roughly the same" was that he says it is roughly the same.
He says pay lot more attention on Content and Logs and work backwards on that, rather than spending time on observing the Datacenters.
Click to learn from Matt Cutts Vedios on Data Centers that was released on 31st July 2006 and more.
I am now skeptical on the results displayed on the three main Datacenters as I throws the same results on SERPs though there is a change in position of my website on the three Google DCs every other day.
