The only problem that I've encountered is that some MORON decided it was a good idea to make FOOD into FUEL
Apart from that, plus the fact that it's un-stable and eats away at rubber fuel lines
, and gums up your carb I've encountered no difficulties after adding Sea-Foam to the tank. If the seals and hoses on your engine aren't ethanol tolerant, then you may want to consider replacing them.
HTH, sorry for the rant.