How nice would high octane gas be?

Here in CA, where all pump gasoline has 10% ethanol at most, the only problems either me or any of my friends have experienced is with lawn equipment or boats that go unused for months without using any sort of stabilizer. From my experience, if your junk sits for months, use a stabilizer, and the 10% EtOH shouldn't cause any problems.

A far as higher octane. Great... If you have a car built to utilize higher octane fuel. Otherwise, who cares?