Excellent point Rockport. I've heard an analogy regarding a deer's nose that goes like this. When a human smells vegetable soup they smell the soup. A deer smells the corn, peas, carrots and anything else in it. So a cover up scent is just a money maker for the company.
Now I've used deer scents and curiosity scents with good results but I must stress when used at the proper times. Just prior to the rut a buck scent can work magic. Any buck in the area wants to check out the new guy to see if he's a threat to his does.
But most of the time I believe no scent is the best scent. Stay as clean as possible and use the wind. The wind can be your best friend or your worst enemy.