I saw these in a store and tried them on. I'm a 7.5, but found the 38 too big (the shape of the sole to my foot). 37 fit well and found the best price here with the coupon offered.
They are very sleek, comfortable, lightweight, and waterproof! That was a big selling point for me. I walk a lot and just got to test them in the rain. Passed with flying colors.
I find them warm, probably because of the waterproofing, so I don't feel like I need room for a thicker sock at all.
Even thinking of getting a backup pair, because you know most companies won't make something more than a season or two . . sigh.