I've looked into this as well. Would be a great option if there were any tuners that tuned E85 around here. This stuff is huge up north and in the plains. Many of the tuners are in MN, ND, etc.
PROS - car runs cooler, inexpensive race fuel options (cheaper than pump gas), burns clean (nice to mother nature), boost friendly fuel for sure when tuned correctly - can make big power.
CONS - fuel system upgrades needed, higher volume needed (generally 30-40% more), different grades of E85 depending on time of year and location so quality can differ, lack of experienced E85 tuners in this area
I will be running E85/E98 in the next year or two once I upgrade to a Big Stuff or FAST system to have 100% control over the fuel/tuning issues.
I just dont know if I can trust the stuff yet trying to run 20+ PSI of boost.