I'm of the yes and no group. I do think at times scent makes a difference while at other times it doesn't matter. But on the yes side, I am more inclined to feel that the Gulp, PowerBait and Trigger-x products do a better job than a simple cover scent. I'll add some of my plastics to a shad colored power bait package and let them stew for a few days and that really can make a difference. I carry the Gulp spray or a bottle of Gulp juice to coat baits with while crappie fishing and that has saved the day for me on more than one occasion.
While we are discussing scent, Tommy Skarlis let onto a handy tid-bit at a seminar I attended. It was his contention that Gulp products are the crappie baits to use while walleye/sauger seem to lean towards the Power Bait products. I've seen this first hand over the years and agree with him 100%. The Trigger-X product seems to attract them all at times, but I have noticed that when the fish are not hitting a scented product, the trigger-X is the first they will ignore. I think Berkley really has the amino acid/pheromone scenting wrapped up nicely and I will use either or as the situation calls for if a scented bait is needed.
One other common scent that works great at times is cod-liver-oil, or that oil that fills those fish-oil capsules sold in health food stores. The plain old oil sold at any pharmacy is cheapest and easiest to use. I have a visine bottle that's been rinsed out and filled with this oil and used as a scent while crappie fishing. I've had that same small bottle for about twelve years now and its in the pail at all times. When it needs refilling I give it a shot and then it goes right back to the pail. The pharmacy bottle of 4 ounces I think cost $4.99. Cheap, effective.
I carry baits that have been treated in the package with anise and the cherry bomb and use them as often as not, but then too I use those that have gotten a shot of the fish oil or the Gulp spray or have been sitting along side some powerbait baits until I find a winner, then I will stick with whatever it is. You really need to keep an open mind when it comes to scent because there are times it will do more harm than good and being stuck on it might cost you a lot of fish.