Ethanol absorbs water. If I was going to run more than what's in the regular pump gas I wouldn't let it sit in my gas tank for long periods of time. At the least I would add some kind of ethanol treatment.
I did a head gasket job an a 96 civic a few years ago, when I took the head to the machine shop, the old timer I know took me in the back and showed me what the ethanol does to valves. The head had about 150k on it so it took a while to show effects. Does Direct injection have a different effect?....who knows.
It's a good bang for the buck if you want more power. I know a guy with a Chevy Barretta big block full drag car. He had to start running E because it made his motor run cooler. It over heated without it.
Just run it nice and hard and don't let it sit in your tank for a long time. It's safe.
Just my .02
