chaco's are VERY comfortable for sandals and most are American Podiatric Medical Association certified.
I wear my flip sandals on a daily basis and never have foot pains that i use to get with other sandals if i wore them too much...
I also bring my flips when im backpacking. they are much more secure than other sandals when doing creek crossings and are fantastic camp shoes. if i was doing an 4+ day hike, i wouldn't bring them, but for shorter trips, they are a nice luxury.
i will never buy keen or teva sandals after trying chacos.