Spook,
I think they have so much surface area they don't mark scopes, at least mine have not. The 6 bolts don't take very much torque to lock a scope in tight.
I can remove scope from rifle and it will return to zero. On mine I was able to use them as is as far as the ring portion. On 1 set the clamp bolt that hits the base was off. I had to reindex it by pushing it out with an arbor press, realign and repress. It may have worked as is, but was an easy fix for me. I didn't even call to return them.
The Burris XTR with the EGW pic rail is an awesome setup for the money. Neither have given a hint of trouble in service.