I can't say that they don't give off scent but I have used them for several years and I haven't noticed deer winding me any more than they use to.
I use hand warmers, toe warmers, and body warmers and I'm a lot more comfortable now.
One trick I learned is that my upper legs get cold after sitting on stand for several hours. I started putting an adhesive toe warmer on my base layer (outside) right above my knees. It helps when you are sitting in a climber and at the end of the day you want to be able to stand up.