My wife bought me the Gerbing heated vest for XMas a couple of years ago and I've used it several times while ice fishing and hunting late season. It's a valuable tool to have in the arsenal - I recommend it.
Battery life is a concern - I bought an extra battery and a charger for my truck which helps keep a fresh battery on hand.
One quirk with this vest is that it needs to be your second or third layer for you to really feel the heat. However, the battery is in the vest pocket so you end up digging thru your layers to turn it on/off or adjust the heat level. Not a showstopper, but something you just have to deal with.
It's worth that minor hassle - I don't turn the heat on until I've sat a while and maybe even begun to feel a little chill, but when I do Oh Boy is that nice to feel the warmth. It has 5 coils - 2 in front by your collarbones, one between your shoulder blades and one on each of your kidney areas.
I was in my ladderstand up here in Houghton Co Sunday morning with the windchill below zero. I pulled out everything in my bag of tricks - merino wool layers under the heated vest, MT050 parka, Stand Hunter bibs, Saskatchewan boots with heat packs under the toes, handwarmer muff with heat packs (hey, what says warm better than "muff"?), neck gaiter, facemask and beanie all under the parka hood. I sat 4 hours till dark thirty with no problem. Heck a cold beer back at the cabin even tasted good so I couldn't have been too cold
I'm hoping all of this will serve me well when I'm hunting late muzzleloader in your great state of Iowa come January...