There's been a number of scientific studies, as well as empirical evidence that shows that there's really no anti knock benefit past E40 - E50. There may be added cooling benefit, but once you can hit MBT, you don't need more octane. Most full E85 setups are done out of convenience in filling and avoiding mixing. There's some debate, but E85 is around 108-109 octane (heck I've seen reports of 113-114). E40-E50, when arrived from a mix of E85 and E10 93, should be around 99 - 100 octane.
Another interesting observation - Matt Happel from Sloppy Mechanics posted a dyno comparison from race gas to E85 - no other changes - timing, boost, afr, nothing - and the E85 setup made more power. Used a hell of a lot more fuel, but made more power.