Any one here ever use the Grabber brand (or other) of chemical insoles in your boots to help keep your feet warm? I'm especially interested in those that are like a full length insole (not just the toe area).

If you have used them how are they to walk in? Do you need to remove the boots regular insole?

I'll be watching this thread too as I've never heard of these.

You can get them from the usual places like Sportsmans warehouse, Basspro, Cabelas.
I've used the ones that you can slip into a glove or mitten and they help keep the hand warm. Also tried the ones that only heat the toes area-did not like them. They constantly moved around while walking and eventually would get in a area that made it uncomfortable to walk.

The full length insole type looks like it might be a great addition to a hunting boot without having to add lots of insulation, but I wonder how they are to walk on?

The only ones I've used are them battery operated socks that are too hot when walking, and didnt seem to work when my feet were already cold. I like them chemical packs that you shake and put it in your pocket. They work good.