Never tried one, as I have a Sporty, but those who have them, clearly are divided on the issue. Personally, I would give it a try, as it is part of the traditional look and feel of a Harley, but old habits (like this old rider) die hard, so like many...choose not to use them or get the kit to "fold'em" out of the way.
Part of the problem is as PigSnot observed and noted, most new riders are introduced to heel and toe shifting not properly fitted, and not used to floorboards as well...a double whammy. Obviously if the standard HD sized rider is over 6 feet and 190 lbs, they are not setup at the factory either. Get it fitted properly to you and ride with patience and effort, I think a lot more riders would use them and like'em...JMO!