There's new reports coming out every day showing that ethanol is actually more harmful on a large scale than regular gas......oops.
GM told us that regular everyday engines run fine on ethanol up to E20, at that point you need a flex fuel engine calibration.
You'll see a bit less fuel mileage (Regular engines see a fairly direct interchange, E10 means a 10% drop in economy, E20 would see a 20% drop, up to the 20% point. Flexfuel engines don't see this change due to calibration, YMMV though, literally.) and a very slight power drop, almost unnoticeable.
As for me..........no ethanol for my truck, though I have run it on biodiesel before!