I agree to nearly 110% of what you all just said.
Premium gas will improve mileage, provided you do essentially freeway miles cruising in top gear.
If you do stop&go city traffic, the cheapest is best, no use wasting premium idling at the lights.
Ethanol is an alcohol, and alcohol is more volatile than gasoline.
In the long run, the ethanol will slowly float to the surface and eventually evaporate.
OR
If you run the bike on last summer's FlexiFuel mix, she'll run on the gas, then suddenly chug, sputter and clonk to a halt as the more and more pure alcohol feeds in the fuel line... Remember, the fuel:air mixture is 1:14 with gasoline, it's only about 1:6 with pure alcohol...
I'd say, FILL the tank with regular to the brim and a good dose of Sta-Bil or whatever.