I've used them on a couple of different leases and it never seemed to bother the deer.
I wouldn't use one if you're bow hunting tho.
That's probably taking a chance that would end up ruining your hunt.
Just remember that you can't leave the heater in your stand when you leave. I don't want you to blow up when you return and light it up again.
Good luck and stay warm.
Quote: "Real men hunt with fly swatters!" - me... lol