Well that depends on a lot of things. Ethanol tends to degrade fuel systems that were not built to handle it. The plastics and rubber lines and such break down over time, and the more ethanol you use, the quicker it happens. You can of course, replace the lines and pump with ones that can handle the fuel, but if you don't it will take several years of use before you run into any problems.
Now when you just add ethanol into the system, you are really not getting the benefit of the ethanol without tuning specifically for that ethanol content. Most people here add 30-40% ethanol and never touch the tune. Sure you may gain a little horsepower within the adjustability of the ECU, but the car still thinks you are running 91-93 octane and will not push the car for the 98 octane fuel it now has. So on an 100% E85 car, you're gonna want to get a tune specifically for E85.
I believe the injectors in this vehicle will flow enough to allow for the use of E85 only, but as you add more and more boost, upgrade the turbos, etc. you may run out of injector, which would of course mean you'd need larger, or more likely supplementary injectors to meet your needs. I don't see this being a problem unless you start going over 18psi or thereabouts, but I don't know that for sure.