I didnt check Ironwoods link, but I think its for Bootblankets, or similar under another name. If so, I agree totally. They are absolutely the only thing that will keep my feet warm, and Ive tried alot of things.
When I first got them I only took one with me to test them. Right foot stayed toasty warm all morning, my left foot was frozen after about an hour and a half. I ended up wishing I had brought both, but I knew for a fact they worked.
Kind of a pain to carry, but thats the only drawback.