I've used a pair for the past ~2 years. I noticed not long after I started cycling (again) that the heel of my right foot drifted in, causing me to develop a hot spot on my foot after ~40 miles. I added the pedal extenders and the problem vanished.

But as flatlander_48 pointed out, you need to pair them with a set of pedals that use a standard pedal wrench for installation/removal vice a hex key. Either that, or know someone who owns a machine shop.