I bought a lead sled to help develop my reloads. My thought was that it would take me out as a factor in testing my reloads. Turns out I shoot just as well without it as with it. So based on my experience, its useful to reduce shoulder fatigue from recoil but it will not make you a more accurate shooter IMO. It also broke my butt plate on my rifle when the padding in back deteriorated without me noticing.
Would I buy one again? No.