The only downside I personally have with it is that you can't let it sit for long periods. If you do it sort of creates this gel/goo build up. If you keep the fuel fresh/run the car often it's fine.

Mine has been on pump e85 for 7'ish years now. I don't even bother checking the % of the fuel anymore unless I'm really going to turn up the wick. Out of all the times I've ever checked the Alcohol %, it's only been off by more then 1% ONE time... (measured at 83%).

From my personal experience it's not as "non standard at the pump" as people would make you believe.