Ethanol, when blended with regular gasoline, is a performance killer. No ifs, ands or buts (IMHO, of course!). The most visceral experience I've had to confirm this is on my sportbike - 1000cc, 180 hp high-revving sportbike (Yamaha R1); have experienced the same on smaller capacity (600cc) bikes as well. Gas with ethanol makes the bike stutter and hesitate, and makes for uneven idling in summer/hot temps - sometimes even has the effect of stalling the bike. Mechanics focused on high performance motorcycles will attest to derogatory effects of ethanol in fuel, in my experience.
While I'm not familiar with chemical properties of ethanol, I have a hunch that it's added to fuel primarily to save the oil companies a bit of money by reducing cost, hence improving margin per pumped gallon. But I have no facts or figures to back this up!