Most small engine mechanics will tell you that ethanol in gasoline is not a good thing, due to the residue build-up creating carb problems. However, that can usually be alleviated with the use a good fuel additive, of which there are many on the market today. Personally, I use Star Tron in all gas used in my small engines and outboards. Haven't had any problems for many years.

The real "negative", if you want to look at the big picture, is from the farmering end. Way too much corn is being used to make this additive (which really doesn't appreciably yield any benefits to gasoline, environmentally or otherwise). That keeps food prices up and availability down. Farmers are paid more to produce the crop for ethanol, than for the benefit of the consumer. You can juggle and jiggle the stats to create support for most points of view, but I just don't see anything positive about it. JMO!