how hard/easy would it be to run the car on it?
Not really a massive issue, so long as the E85 is compatible with the fuel lines, injectors, seals etc etc.. As some E85 will corrode those parts if left sitting for a while..
It would just be a case of possibly optimizing injector size (depending on what turbo you are running) and flow rates etc, then mapping the car to make the most of it, so you would be able to run a fair bit more ignition advance because of the low temp of the combustion and the high affective octane rating.. (up to 120 Ron)