I've never noticed a HP loss either riding or by dyno. In my case, it reduced fatigue associated with 'manhandling' a large quad and it gave me improved control. I wouldn't think of it. I have a great deal of respect for the inventor of the product. I love it when people figure things out and it seems to work.
Many people seem to favor the pricey devise.
However, in my application it is not indicated. Wheel spin is not a problem. In other words, a torque monster. Remember here that we're used to a 17 hp Blaster, with no Amp Link. The Banshee used up chains at an alarming rate and our friend had no base line to judge that by, because he put the Amp Link on the Banshee while the motor was out to Trinity being rebuilt.