Sandles are great for the time climbing, but ithe only complaint I've heard both times so far was while hiking out in the dark.... "Gee, I would've liked some stouter shoes" ...
SO, for those who want to carry extra stuff, bring yer flip-flops, cause like Special said, they are cooler and easier to slip on and off. OR, if you are really comfortable hiking in your sandles, go for it, just don't say I didn't warn ya...