I'm on my second pair of these, but they are by far my very most favorite shoes ever. I have high arches and have to wear orthotics in my hiking boots, running shoes, etc. but these Chacos give me just as much support, plus the grip of a running shoe (or at least a really good technical sandal). I walk between 1-6 miles a day in these to and from the bus stop or to and from the office, and could easily walk even further in them if I needed to. They may seem pricey for a flip-flop, but they're worth every penny. I'm on my second pair (puppy chewed the first a couple years ago, otherwise I'm sure they'd still be going strong), and they're wearing great, two years in. They're also great if your feet sweat b/c the suface is non-porous (to the naked eye, anyway) and these don't smell or get spongy they way some flip-flops do if you sweat in them. And if they do get dirty or stink, you can just scrub them off in the sink, no worries.
Fit: I wear a 9 in my Vasque hiking boots, North Face running shoes, and other shoes generally speaking, and the 9 works fine for me in these Chacos. My feet are on the narrower side of a regular width, but they seem to work okay for my mom, as well, and her feet are size 9 but wider.