I saw them on a guide's feet on my cycling holidays last year, so they seem to work and stay on fine.

Might be a better option than a full bootie because they do not trap humidity as much, as you say, the problem is mainly the toes, the rest of the feet might be served with wool socks.

Personally I wear windproof socks but I get slightly chilly toes still.

heh. see what gadgets the bike fair tomorrow will have in store for me.