Thanks, everyone!
Caro, you're right -- there is no cushioning on the soles of these. I have worn this kind of thing successfully before, but I plan on testing them out around the house as much as possible to be sure.
vipanchi, it's funny you mention Birks! I slipped one on in Nordstrom last night while returning my unsuccessful white sandals, and I could not take that shoe off fast enough. Clearly they are designed for someone with feet very different from my own, because I experienced zero comfort. Funny because they're so known for comfort. But I actually get what you mean -- these sandals are flat, with broad straps across the foot, and I like that. The overall look is trend-current, but this version is more comfortable on my feet and with my style. I just felt like I had a big flipper on my foot in the Birk.
Suz, Mona, and all re: the flatness. I actually think my most comfortable footbed is a small heel, but flat is not a deal-breaker at all. Two of my favorite summer sandals are flat, although my Cole Haans have some cushioning. I also have some flats that have no cushioning that I wear for full days, but the advantage of a closed flat is that I can add insoles -- not much of an option with a sandal! If these end up being my favorites of the ones I've ordered, I'll have to test as much as I can around the house and then take a bit of a risk that the total lack of cushioning on a flat sandal won't end up disappointing me. My feet are not fussy, but they are a little fussier than they were, say, ten years ago.
Thanks for all the feedback! I love the aesthetic of these. We'll see what the Rag & Bones look like when they arrive too...