My Harley Davidson motorcycle actually get just a bit better mileage (or it definitely seems so) on the 10% ethanol gas. Probably the carb is jetted more favorably toward that mixture... I don't know.
There is actually less energy in ethanol than in gasoline, so it stands to reason that mileage would drop off some... but again, I've not seen it in my motorcycle, and haven't yet checked my 1993 Escort to see how it's fairing on the ethanol gas... probably a bit worse I'd guess.
I know that at least for the time being we're going to be seeing ethanol in the gas. Our tanker trucks (I manage 13 of them in the Virginia area, and also drive one) are hauling a LOT of ethanol from Denton, NC from a railroad pick up point there to the gasoline terminals in the Greensboro, NC area. Our trucks haul about 8 to 10 tanker loads a day to the Marathon terminal there, and we're only one of several carriers doing much the same thing. I'm not sure how many total loads of ethanol are going to that fuel terminal a day, but would guess it's about 30 to 40, which of course is blended into gasoline to get the 10% ethanol mixture.
The fuel tankers have to have the correct gaskets in them to seal the ethanol into the trailers. If you have the old cork style gaskets on the discharge heads, the ethanol will eat through them and begin seeping out. The stuff practically vaporizes almost on contact with the ground. If you spill at small amount when you're disconnecting the hoses you can watch a 12" puddle on the ground evaporate in a less than a minute... then it's gone.
Dan