After about a million threads on hunt forums you can probably still get someone fired up enough to debate you as to their effectiveness. In my opinion, the greatest advantage if any type of product is found if it instills confidence in the user. A confident hunter will sit still longer, If camo, scent lock, cover scent, or another product help to that end then they are worth using.
I used scent lock for a while and then I stopped for two reasons. First, the pants I had were hot and didn't have button legs. You had to take off your boots to get them off and they were uncomfortable to wear without a pair of jeans on under them. It was a pain in the neck to slide them off after an archery hunt.
Second, there were so many negative threads that I started to doubt the effectiveness of it. The comments that made the most impression on me had to do with the fact that most modern home dryers use a heat senser to regulate the need for heat as they dry clothes therefore they never achieve a high enough temperature to reactivate the carbon in the suits. I have no idea if that is true, but I heard it enough to start doubting the effectiveness of the product.
The bottom line is that confidence and mental attitude are a key ingredient in making you sit longer and seat-time is directly related to hunting success. Products like scent-lock serve best by marketing confidence.