Right now I am using E85 every day in my 09 Ford Expedition, I normally use the typiucal 10-15% ethanol blend. I have found that the engine idles more smoothly on the E85 (it is old and idles rough all time now). As far as gas mileage goes, I normally average ~14.5 mpg on 10-15% ethanol and on the E85 I have been averaging ~12.5 mpg, so about a 14% drop in mileage for me. However, the E85 has be about $1.50-1.75 per gallon (~$3/gal for E85 ~$4.6/gal regular ethanol), thats ~35% cheaper in Ames.
So even with the the loss in fuel efficiency, I am still saving ~20% on gas by using it RIGHT NOW. The savings aren't always this good.