I feel somewhat guilty and conflicted about Luna Sandals, because on the one hand, I'm not recommending them, but on the other hand, I use them all the time.
It's all about the price.
I want to like Luna Sandals, because the company was started by Barefoot Ted, one of the runners featured in the mythic book Born To Run by Christopher MacDougall. I bought my first pair from him, when it was still a “one monkey operation,” and his huaraches were super thin and rubbery.
All of the Luna Sandals now are thicker, at least 6mm or more, and some now with some hardcore treads. My first Lunas are long since gone (the knot at between the big and second toes finally wore through the rubber. I now own a pair of the 'regular' 6mms with the leather laces. Actually the leather laces are from my first pair. I ordered this pair with the hemp laces, thinking, that since hemp supposedly tightens up when wet, that they would be good for Portland, Oregon running. But the hemp laces just never felt good, despite not ever having to stop and relace like with leather laces, and actually broke off at the toe joint area on a long cold rainy run, and they are almost impossible to re-thread when wet, and when one's hands are cold, and when one is dehydrated, and losing sunlight.
My other pair of Lunas are Leadvilles, slightly thicker, though also slighty more spongy—I'm not sure of the exact composition. And it's this pair that I've actually used on two trail marathons in Forest Park, where the gravel fairies have been busy on the trails, and also Leif Erickson road is just awful with gravel and rocks. I opted for the Leadvilles because of thickness, to just give my feets some sturdy cushion. And they performed well, because both races were during dry weather.
All huaraches do poorly in wet conditions. If the tops get wet, then my feet slide all over the place, causing the laces to dig into flesh, and making any kind of incline, up or down, hard to get traction on. For wet conditions, my go-to minimalist footwear is still Vibram Five Fingers, the KSOs. They cling to the feets well, wet or dry.
The best thing the monkeys at Luna did was come up with a cool, practical, new sport lace, the _____, which is partly elastic, so stays snug, and doesn't need re-tying, and makes slipping huaraches on and off easy. As with everything at Luna, it seems pricey, at $15, and if it were the only option I'd pay it. But Xero Shoes now offers a similar sport lace.
That said, there is something to be said for the tradition leather laces. I just like the gladiator look, and it tends to make people do a double take. And, when tight, the leather wrapped up around the ankles seems to provide some stability, which most minimalist runners shouldn't need, really, I guess. I do always have to stop on a run with them, and re-tighten the laces. The leather just stretches out. So, if using them for a race, try and wear them with plenty of time before hand, and may even go for a light job, then readjust right before the race start.
Many people like the look of Lunas, especially with the sport lace, and use them for a more sporty casual look around town. They look kind of like Tevas or Chacos, say, but with a way thinner sole. You can get some models with an additional leather top, which make them look more traditionally sandal-ish, and may make them less slippery (I've even heard of people putting surfboard wax on them to prevent slipperiness). And, I do like the look, and sometimes just walk around in them. But I find, for some reason, I'm not sure why, that when I walk around with them on pavement in the city that my heels get a soreness, almost plantar fasciitis-y. Maybe it's something to do with the sponginess, or maybe the thickness lessens my foot sensitivity and I lapse back into longer strides and heel-striking.
The main, and best, way I've used my Luna Leadvilles (with sport laces) is for backpacking. I wore them for my two recent epic trips down into the Grand Canyon, with great success. With an extra 40 pounds on me, I can't be as nimble-footed as I'd like, so still wanted some thicker soles, while also, because of the heat, being able to have natural air-conditioning on my feet. I did manage to both freak out and impress my hiking companions, all of whom still opted for boot-coffins. Again though, on the one trip, in which there was some wet muddy trail, when my Leadvilles got the least bit wet, my feet would slip all over the place in them.
So, with all these good things to say about Lunas, why am I not recommending them. Well, the price: Almost a hundred dollars, or more, for most models. And, Xero Shoes offers some equivalent models for almost half the price. Xero also still offers a thin-soled huarache, and Luna does not. Xero Shoes now also even has a sport lace similar to Luna's. Some of Lunas more hardcore models do have some super tread, but if that tread is supposedly for maybe wetter muddier conditions (though may just be about looking gnarly and cool) then your feet are going to be slipping around on top anyways.
But, I bought my two pairs of Lunas before Xero Shoes was even in business I think, and they're still basically good, good products. Which counts for a lot. But I think also the mystique of Barefoot Ted and Born To Run counts for their popularity too. There are other huarache brands out there—Xero Shoes are the only ones I've bought and used. As someone with a limited budget, I just can't afford to buy all of them, nor even opt for the 'cool' expensive ones.
If you buy Lunas, you won't be disappointed. Just know that Xero Shoes huaraches, for example, are almost half the price.
[also note: the best way to learn to run in huaraches is to run barefoot first. Do NOT run in huaraches like you would in 'regular' running shoes. Keep a shorter stride, smaller and quicker steps. Just go slow at first, and use them on trails. For pavement, you're better off barefoot anyways]