If you're asking me - I'm still at that spot where running E85 is a wash in terms of cost per mile driven. E85 is somewhat expensive in Austin, although not to the scale of 93 octane fuel.

I haven't gotten back to playing with it yet - mainly due to the local availability. I will say that it can run in a much wider AFR range than gasoline, so I can go much leaner with it under cruise to see if I can recover some MPG.

Good things:
1) It's much cleaner for your motor. Heads/blocks run on E85 look really good once opened up.
2) 100 octane. This won't matter to most people, but on a turbo truck like mine, it's absolutely great and means more power as I can run more boost and more timing.
3) Increased exhaust gas - again, on a turbo, I boost faster.
4) Cleaner emissions. When I need my annual inspection, I'm probably going to run on this stuff.
5) Lower Exhaust Gas Temps

Disadvantages:
1) Availability. At least in my area.
2) Environmental wise, it's probably not *the* solution to our foreign oil dependence as it requires a lot of energy to make it and decreases our food supply.
3) Decreased fuel economy.
4) I believe it requires retuning - in some cases this could be just an increase in fuel pressure.