Quantcast is the only one on the list with code embedded in the site making it positively the most accurate. - Charlie Anzman

Charlie, for everyday use, absolutely. I'm surprised more people don't use Quantcast - Duncan Riley

Charlie - Quantcast only works if everyone uses it - without that, comparisons will be off. If everyone uses it, it would totally rock. Then we would have different questions to ask like around page refreshes to drive pvs. - Allen Stern

I like to think, though, that quantvast's correct data gives it greater insight into approximating it's estimated data, the special sauce the others don't have. - felix

and when I say no one, I except Google's entry. :) - felix

webtrends if u have the money - adolfo foronda

Allen, true, but it's at least a start. If we're unhappy with the results, we can add the code, and that wins brownie points for me - Duncan Riley