I have had a Heater Body Suit for about six years. Yes they work very well, especially in the wind. I have sat all day in the rain and stay warm and dry. They are a bit of a pain too get into up a treestand but now I just put mine on and climb with the suit on.
If you are planning on sitting all day or at least a half a day good investment. Once you put it on you have to stay where you are located until the suit is removed. Kinka pricey but well worth the money. Keeps your hands warms also without the use of gloves, very easy to unzip when the time comes for a shot. I started taking blood pressure meds about four years ago and can not stand cold as much as before so I used now more than ever, ask anyone who takes blood pressure meds and they will tell you it seems as if the temp has drop 10-15 degrees.