I'm definitely all about the foot temperature thing - if my feet are cold I won't get to sleep, if they get too warm it's liable to be one of the factors in me waking up and not being able to get back to sleep until I fix it. I have several pairs of bedsocks but my favourite ones (which have some fancy wool mix that I can't for the life of me remember what it is, maybe angora but I think something less common than that) are starting to wear out, which is tragic.