As far as I can tell, E10 sells to two sorts of people; those who never track their fuel consumption and don't realise the increased consumption swallows the cost saving several times over, and those who cannot yet afford a hybrid but think they're making a difference...
Like this bloke?
E10 was 9 cents per liter cheaper today than other unleaded fuels. I agree with this article, If the price difference is greater than 4cents per litre. For me, in my car, E10 is cheaper and all I use.