I actually like running E85 when I can get it (usually back home in South Dakota). We've calcualted cost vs. mpg running 89 and E85 and depending on the market, even though the mpg number is lower it can be cheaper. But usually not by much. Plus it smells good!
Edit: There are more and more racers in my area converting to E85 for track use because of it's resistance to detonation. Not cheap to convert your fuel system because of the extra volume of E85 it takes versus gasoline to run stoich (9.7-1 vs 14.7-1 for gas)...by the time you're WOT, you're pushing a lot more fuel to maintain proper A/F, but the extra power you can make by upping boost/timing/compression makes it worthwhile...especailly since you're no longer paying $7 a gallon for race fuel.