Dave, your general contentions are correct, to a point. The first, the fuel tax deal governments benefit from due to decreased mpg, is not long lasting. Cummins, GM, and others have engines in testing phase right now, that get better hp and torque than current crop of engines, at a lower displacement, along with as good or better mpg than current engines running gas, and doing it all on E85. GM's 3.2L EBDI engine in testing now, gets the same HP and Torque as the 6.6L Duramax diesel, and better mpg, on E85. Cummins 2.8L inline 4 banger, currently in testing, has 450 lb torque (better than most small V8's) and as good or better mpg, again, from E85.
Phase separation can indeed happen. Does it happen frequently? Not that you would notice. Folks in the midwest, with their wet winters, and humid summers, have been using ethanol blends from E10, E20, E30, on up to E85 for decades and phase separation is something that hardly ever comes up. Most folks have no clue what it is, and if it were occurring frequently, they would. True, ethanol will blend with water and cause phase separation, but unless you are introducing water into the fuel tank, it is not really an issue. All vehicle fuel systems and tanks are closed, non vented systems. My advice... don't pour water into your fuel tank. Only put fuel in it. Some marine and small engine problems could occur, but usually because of long term storage in the tank and vented tanks. That is a recipe for condensation issues, and that could cause a problem combined with ethanol. But it could also cause a problem even with regular gas. Now, I will concede that a fuel station could have issues with their storage tanks and it cause a problem. After all, we do not live in a perfect world. But it sure seems to be extremely rare.
E15, it is still too early in the game to make a full conclusive determination if it is a problem. The USDA and DOT have done a lot of testing and not found any conclusive data that shows E15 is a problem in vehicles produced in the last 10 years.
True, problems with ethanol can occur, just like they can if someone gets a bad batch of gas or diesel. The ethanol folks have had a standing offer to pay off anyone with, best I recall, $250,000 if they can prove conclusively that an ethanol blended fuel actually was the prime culprit in a fuel related problem. So far, no one has won the prize. Usually it is found that conditions that had nothing to do with the ethanol itself was the true culprit. like vented fuel systems, improper storage, etc.
I have no issue with anyone who doesn't want to buy the stuff. I have no dog in that hunt. I like ethanol blends, and have used them in everything from lawn mowers, chain saws, generators, and vehicles for a long, long time, with not one fuel related problem. But I do somewhat take issue with arguments that are based on internet folklore or some rare situation that we do not know all the facts surrounding the case. If ethanol were such a problem, there would have been a hue and cry come up from the public a long time ago. But except for a few outspoken folks and the oil companies themselves, you hardly hear a peep from anyone else. Day after day, year round, for decades, a high percentage of the buying public have filled their tanks with E10, at least, with hardly any issues occurring.
It makes it real hard to buy into the fear and conspiracy regarding ethanol.