Thanks Steve. I was trying to answer the exact questiion you said for myself. I more, or less, stumbled across this by Googling. By the way, I always check for results on www.Google.com , and www.Google.co.in , just to see the results for India.
I pull my keywords from overture still, and assume that there are variances. Its pretty easy to guess which keywords have a huge search volume when you compare the OVT score to the # of results in google.