"In some ways I see it as being about as pertinent as IQ to measure 'smarts'."

My gambit is, I admit, purely anecdotal, but my observation (having lived in various parts of both the US and the UK) is that, conversationally (and I stress this because I don't think the phenomenon is nearly as pronounced within written English as it is in spoken conversation), British people tend to be more articulate, with their vocabulary both more precise and more diverse. The thing I think is particularly interesting is that, with Americans, even well educated and "well bred" people have a similarly casual approach to language. I think it is amongst the upper and more educated classes that the differences are, if anything, more pronounced.