The only place I saw an issue with shoes was Soarin'. My niece only wears flip flops during the summer. (I know, she'll have back problems when she's older but try telling that to a 16 yr old.) Anyway at Soarin' they said she had to leave her shoes on the floor and they'd be waiting for her when we landed. It was as promised. When we landed, her feet slipped right into her flip flops.
I agree with Nanasfan. I am pretty sure (just having my first coffee, so hopefully I'm not too foggy) that all the rides other than Soarin' have floors in the ride vehicles. The only thing I lost on a ride was a hair clip on the Rockin Roller Coaster.
If Disney didn't let people wear shoes without backs, they'd lose about half of their customers, being that it seems as though everyone wears either Crocs or flip-flops!
I wore my Mammoths in December and didn't have any problems. They ask you to take off any shoes that aren't sneakers on Soarin, but it's more fun that way.
I wore them last September when I went to Universal instead of Disney. I know, I know. Anyway, I put the back strap on when I rode Dueling Dragons, besides that I wore them with no problems. I assume it would be the same at Disney.
Wore them the entire time last month with no problems at all, I just put the backstrap up while on Soarin. It was my 1st trip with no blisters, no tired legs or feet. Have fun!
I wore them last year and never had a problem. Mine has the back strap on them to..Let me just say that I was one of those people that wouldn't be caught dead wearing them because they aren't to appealing, but let me tell you...they are soooo comfortable and they saved my feet from my sneakers that were killing me. My family said to me, why spend the money on those crocs that you will probably never wear again? I actually wear them all the time now...I havent had the guts to wear them to my college yet though...
Back in October, the only shoes I wore were Crocs (or Crocs flip flops), and the only ride that I took them off for was Soarin'. And nobody really said anything to me; I just followed the directions. Who knows? I might've been able to get away with keeping them on...
I got mine just before we did our Land/Sea vacation and they were fabulous, on both land and sea! They can get wet and are still comfortable, never hurt at all-- I'd recommend them.