So far, I have used 1091 gallons of E85 in my ST this year with absolutely no problems.
You don't have to mix it 1/2 and 1/2 like dbk774 suggested. If the vehicle is flex fuel capable (like my '04 ST) then it is will burn any percentage of ethanol up to 85%.
I do know several people that use any percentage of ethanol up to 85% in their non-flex fuel vehicles with absolutely no issues either. They say it is corrosive with some metals and deteriorates some rubber gaskets, so we'll have to see what the long term effects are to those vehicles.
Yes, I do get less milage. Probably somewhere around 13 mpg. But I don't keep track cuz a lot of my driving is local around town so it's terrible whether I use regular gas or E85.
The price of E85 here is consistently 30-40 cents less than the 10% ethanol blend which is usually 1-2 cents less than regular unleaded.
So, I think it's pretty close to a wash on my cost per mile with E85 versus regular unleaded. And in the winter (depending on the part of the country you are in), the E85 blend is usually reduced to somewhere around E70 to assist with starting the engine in the cold. However, I've started my ST at -20 F without a block heater or anything else without any trouble.
As far as clogging your injectors - I suppose there is a small amount of truth to that. From what I've gathered, that rumor is still around from when the 10% ethanol blends started appearing. And back then, regular gasoline wasn't as refined and had more impurities and other gunk that caked in your fuel system. The ethanol in the fuel acted as a solvent and knocked that stuff loose - therefore clogging fuel filters and possibly injectors. However, I highly doubt you would see anything like that any more.
So, assuming that the E85 fuel that I used this year averaged out to about E80 due to the winter blends and driving more in the summer, I used 873 gallons of a renewable fuel and only 218 gallons of unleaded gasoline.
Then there's the naysayers that complain ethanol takes more energy to produce than it produces. I can't dispute that fact, however, I'm betting that is also a held over fact from long ago and not true of the modern ethanol plants. The by-products of producing ethanol are also used as livestock feed and the carbon dioxide created by the yeast is often captured to produce dry ice among other things.
And yes, it does receive some subsidy from the federal government. But name an industry that doesn't receive something in some form or another? health care, airlines, railroads, just about every type of agriculture, etc. So, since our taxes are paying for the subsidies, why not take advantage of them and at least attempt to reduce our oil imports?
I don't believe that ethanol will be the complete solution to our energy needs, but it's a start that is pretty compatible with our current needs and use; it is stored, pumped and burned in our vehicles just like gasoline. You can't do that with hydrogen or other alternative fuels yet.