I had this same quandry last year when hunting in Minnesota in late November and December in ground blinds. I considered the heater but told by many it would work well in a wood or box blind where you can close it off but not so much a pop up where you have the mesh windows open.

I've never had a problem staying warm with my cold season hunting clothes, except for my feet. I think that's the problem with most people.

I've tried all sorts of sock combos with very well insulated boots but I'd still be dying after a few hours. Then somone suggested I look at insulated boot covers ($40-$50). I tried them and they work wonders. I can be on stand or in blind from sun-up to sun-down in below freezing temps and never get frozen toes. And if I drop a heater pack in each boot cover, my feet usually stay as warm as they would be if I was inside watching TV.

If you're going to be sitting still, I'd highly reccomend them. They slip on silently, fold up nicelyand weigh about a pound total for packing in. I'd also reccomend bringing along an old board or carpet remnant or something so you can put your feet on them and not on the cold frozen ground. Can make a big differenece.