I started riding when there was no such thing as a heel shifter and I could never, ever use one. It just doesn't belong. Had mine removed before it left the floor.
This happened to me in Canada over the Summer, came up to a stop light with my woman on the back, was able to break it loose right before hitting the point of no return. I couldn't believe I prevented the fall, but luckily I did. I will be taking the heel shifter off soon.
I removed my heel shifter on my '02 Fatboy. Personally I would rather do all my shifting with my toe. A friend of mine had warned me about getting my pants leg caught on the heel shifter, so off it went.