We have two. They are great for load development as it is very steady. I've found that it isn't great for sighting guns is on though. For some reason your point of impact will shift about an inch at 100 compared to shooting off a rest. I did some research into it and found that others had this problem too. From now on all our guns are sighted in off sandbags.
exactly , because the gun doesn't recoil the same
I am of the Appleseed train of thought sight in with your rifle , prone with a sling because it is what you will have with you when you need to make the shot.
if a lead sled makes shooting enjoyable for you , rock on , it isn't necessary and it does give a different POI vs no lead sled
to each their own , it will depend how much you use it if it is worth it.