Everytime one of these threads come up about what kind of shoe to wear to WDW, I always recommend the Teva Mush. I absolutely love them and always carry at least a couple of pairs to switch out. I am a flip flop diva and live in flip flops around here just about year around, and have probably over 200 pairs of flip flops. I wear all kinds around here, but the best I've found for WDW are the Teva Mush. I also like the Teva Olowahu, Ulani, and Toolani, but not at WDW. My feet have a tendency to swell at WDW and I can't wear the flip flops with the narrow straps. The wider straps just feel better. Another good flip flop to wear down there are the Montrail Molokini. They are more expensive than the Mush, but you bake them in the oven for just a few minutes then immediately put them on and wear them. They mold exactly to your feet and feel sooo good.

I have a friend who swears by Nike Celso, so you might want to check those out too. Teva Mush are by far my favorite flip flops though.
Alot of people on here love the Croc flip flops. I have several pairs that I wear around here, but don't like them for WDW. The toe piece just feels too big and stiff. For WDW I prefer flop flops that have wide cloth straps and a soft cloth piece for the toe thingy.