Smoking and hunting. The smoke itself I doubt is an issue, in fact it may be a very good cover scent, however, smoking while on watch is an issue. Not for the smoke, but for the movements involved in doing so, along with the usual hacking cough that a smoker generally gets in time.
I am not a smoker and never have been, but I have pretty much always hunted with smokers.
Same thing with the modern toys, candy bars, coffee etc, they all generate motion. Deers eyes are different than human eyes, they are designed by nature to spot motion, and can do so many times better than any human.
Take those things, sure, but use them when the hunts over, or you really, really need it, remembering that the deer can see even the tiniest movement from far, far away.
Can you walk up on a deer in noisy conditions? sure, have done so many times, but generally it won't be a big buck, (but even that can happen) Deer, like all animals seem to get lost in what they are doing sometimes, or, they are making enough noise walking themselves that they cannot hear you.
An example of this is when a deer is running in dry leaves. They make so much noise themselves, that you may have to yell at them several times to get them to stop.
The number of times that deer have jumped up at close range on me and escaped you would find hard to fathom. They will lay down and let you walk by mere yards, even feet away, even if you have dogs with you.
Here's one from the camp history books:
five guys have been on watch in the bush, while a sixth guy does a push to them. Nothing came of it, so they all go back to the boat to head down the lake for another hunt elsewhere. They are stumbling about, getting into an aluminum boat, unloading and casing guns etc, when suddenly from behind a small bush, apparently standing in the water at lakes edge, a Doe jumps out ten feet from the boat. The dogger stuffs a shell in his shotgun, takes a quick shot, misses, and dives on the ground, yelling shoot, shoot!
Everyone is unloaded, no shots are fired, not that they would have fired over the idiot anyway.
It's checked out, and the miss confirmed as clean. Such is hunting, deer hunting is exciting.