I have not had any noticeable problems with my fuel (knock on wood). I recently started using mid-grade fuel (opposed to the regular I was using) in my handhelds and noticed that they start easier now.
I do use quality fuel and not just whatever I happen to come by or can get the cheapest.
'07 Chevy 2500HD
2010 John Deere Z925A 54" MOD
2011 John Deere Quik Trak 647A
John Deere walkbehind