I won't use one to sight in my hunting rifles. I want the rifle to be as close to what I use in the field when getting ready to hunt. Mine don't shoot the same off of a sandbag either. I've got a small pillow that I shoot across when working up final loads for a hunt. I've found that loads sighted in over it shoot the same as offhand in my case. I always shoot a few taking a steady rest with my hand under the rifle to check it afterward and it shoots close.
I've always worried that the extra recoil of heavy rifles is transferred to the rifle stock and sled instead of the shooter. Has anyone heard of stock or bedding damage caused by the recoil transfer? If heavy rifles need reinforcement to handle some magnums without splitting I would think the Lead Sled would increase that likelihood. I don't have one so I can't say.