We have about a half dozen Stihl products at my workplace and have not suffered any noticeable ill effects from E-10 (Knock furiously on wood). Some of our stuff even sits for a month or three with fuel in it....I'm trying to eliminate this practice.
Boraticus, here is an article from a guy that runs a top notch chainsaw safety company. His e-book is outstanding and worth every penny (very reasonable price, IMO). BUT...in supporting his company, he does sell stuff and promote his supporting companies. Yes, he sells and promotes that "canned 2 cycle gas" stuff. So, his argument is obviously biased as evidenced by the shameless plug at his article's end for the use of "pure" 2 cycle pre canned fuel (outrageously priced).
But, there might be a few tidbits of truth hidden in his views. Take it for what it's worth. Again, I haven't had the problems others speak of...yet.
Here's his article:
http://www.forestapps.com/articles/two_cycle_fuel.html
Just trying to share info for intelligent discussion/disection. In one of his recent e mail "notes", I think he implied that the switch to e15 might cross the threshold of 2 cycle carbs, but I didn't save it and can't remember. He's big on the idea that ethanol molecules are bigger and more difficult to pass thru the jets and can result in lean conditions.
Edit: here's his other article:
http://www.forestapps.com/articles/Fueledbyethanol.htm that states:"Alcohol in the fuel requires more flow to maintain power needs. In two cycle engines the fuel flow can also relate to lubrication needs. It takes a more open, counter-clockwise adjustment on the screws, to allow enough fuel to run properly. Most carburetors will adjust 10% to 12% but will not accept any higher percentages very well. You should try to a locate a gas supply without ethanol if at all possible."
Don't know if I can trust his info based on his writing (pitching style).