They definately help alot, I'd say they make about a 20-30 degree difference. They are a pain in the butt to carry around though. I'm trying out the Artic Shield version now and they are much more compact, but I doubt they could be as warm and are harder to get on (not as slick inside). I hate putting toe warmers in my boots, feels all cramped and wadded up, so I put them on top of my boot toe and inside the boot blankets and you can still feel the heat come through the boot (that probably says something about the insulation of my old boots).
I also just got a new pair of pac boots, hoping to eliminate the need for either one. I already carry a rediculous amount of junk into the woods!