I feel that some people can get caught up in the whole scent control/elimination scene, to the point where they spend lots of cash each and every year, when plain ol' common sense would suffice. However, I also believe that if you have the money and the dedication to properly use these products, they can't hurt. Problems arise when people place too much stock in their scent control gear, and start making absurd choices for setups (i.e. upwind of deer).
I try to practice sound scent management myself (showering with odorless soap, washing gear in HS detergent, regularly spraying down in the field etc.), and I have had mixed results. I've had deer directly downwind of me that behaved as if there wasn't a human for miles around. Most of these deer were either wet behind the ears, or entirely preoccupied with the rut. They might have smelled me and didn't care that I was there, or perhaps they had not yet associated human scent with "danger".
I've also had deer wind me right away, regardless of the fact that I took several extra steps to control and minimize my scent.
As was said earlier, a good scent control regimen probably helps to give you those few extra seconds you need to adjust to a less than ideal hunting situation, but I firmly believe the only tried and true way to be sure you won't get busted is to mind the wind at all times.