I have to agree with Steve. Deer can smell far better than we can. It's just the way it is.

I do agree that in some cases using cover scent (wind blowing towards where the deer are coming from) can be very beneficial.

In most cases though, it's really not needed when you do a few minor things to keep the gear not from being saturated in human smells.

Really, my family and I have seen better results by keeping our hunting gear outside in the hunting season so the different smells that we create (mostly from cooking) don't soak into the gear. Doing that alone has made a tremendous amount of difference. More than using, or not using, cover scents does.