Switching to E85 is a great way to get some more power out of any engine with boost. This is something that has been thoroughly documented everywhere on the internet. Seriously, there's so much information out there that it's not even worth going into detail about it here.
The two biggest issues with e85 are probably its limited availability in certain locations and it also requires a strong fuel system to support it.
Typically a car will use about 33% more fuel with e85 than with straight gasoline so your fuel range and gas mileage will be decreased. It's tough to say exactly how much though because e85 is not always 85% ethanol, it can range between 50-90% depending on the station.
If you're ready to switch and you're looking for tuning information then go ahead and look at the e85 tuning page: