I have. Last few years I have loose fitting super thick socks that live in my sleeping bag. Only used for sleeping. Loose is important, circulation&dead air space are key.
Yes! REI has down booties that usually go on sale this time of year... probably not the best out there but they are the best buy. Last year, the deal was so good that I bought two pairs and still have one in the box.
I have a pair, for whatever reason I find a dedicated pair of dry wool socks feels warmer. Not sure if it's because the Down gets crushed by the other insulation or they don't absorb moisture off of my feet but I don't even take the down booties anymore for sleeping.
got my wife and I each a pair from Goosefeet; a must have for winter camping imo- if you go that route spring for the over booties- you can wear them around camp that way (or for when the late night urge hits)
I always keep a pair of down booties in my sleeping bag, when I need them they are always there. I can't remember the name brand but they are a small piece of heaven when you have cold feet.
I got a pair of western mountaineering flash booties off backcountry.com that I wear in my 35 degree bag. It's amazing how much warmth they provide for only a few ounces. I did get a size larger so the synthetic sole wraps over my toes to keep them off the bag. With the booties, 35 degree bag, and puffy jacket I got down to the high teens.
yeah, essential equipment. you wake up in a 4 degree wall tent at 2am realizing that your anatomy isn't holding up like it use to and you have two options 1)lay there having to take a piss but knowing you won't sleep for the next 3 hours, or 2) jump out of your bag, run for the door for quick relief and back into the bag for some awesome, bladder empty rest.