Alot of people here on the DIS swear by them, but I am not a fan. They felt really comfy when I first put them on, but killed my arches after a couple of hours. If you are one that can wear them,
Amazon usually has them for a good price. I bought two pairs from there several years ago, after someone here on the DIS recommended them.
OluKai Ohana flip flops are the most comfortable flip flops I've ever found for WDW. I can wear them all week, every day with no problem at WDW. However, they do have fairly high, very supportive arches so may not be for everyone. I have high arches with plantar fasciitis and they work wonderfully for me.