I'm running nearly 100% E-85 right now. I need to put in a couple gallons of gasoline per tank to get good cold weather starting.
The car loves E-85, and so do I. Burns cool, produces about 5% more power, and after months of use ranging from 20% to 100% no signs of problems.
Ethanol only damages un-anodized aluminum that is constantly wetted by the fuel, IF the fuel is contaminated with water. Modern fuel systems being sealed make that very difficult. The WRX fuel lines are steel as is the tank, and the aluminum intake manifold has no problem at all with it as is not continuously wetted.
Corrosion was an issue with carburators where the fuel sat for extended periods in an un-anodized aluminum carburator.