Whitey - 6:35 am on Nov 24, 2011 (gmt 0)
I haven't found any intelligence that can be relied upon.
Today I did a check for Google organic search traffic on a well distributed SEO intelligence tool ( sorry can't mention it here ) ... one of the best. Thought it was great on a couple of sites i know well ... the traffic numbers, dates + other data all corresponded. But as i expanded to other sites i also know well, it started to become wildly inaccurate.
So you may get lucky here and there, but if you want accurate data go and work for Google and get permission to draw on their data. Otherwise, at best it's indicative.