Chyna Whyne is an entertainer and an Alexander Technique instructor in the UK (Alexander Technique is a method for improving posture, among other things), and she specializes in teaching women to walk in high heels.

She has a test that she performs on high heels to determine whether they are stable enough to walk in, and I've posted the video below. She calls it the rocking test. It's very interesting! I found that my easiest heels to walk in (Okalas, Aquatalia Rhumba) pass the test with flying colors. Maybe this is why the Okalas are so comfy for people?

https://www.youtube.com/watch?v=ozicN4KgB9U