I really like mine, I would rate the zero stop as "decent". They use shims for the zero stop, you just keep adding shims until it stops as close to zero as possible. You'll probably get it to stop within a few minutes of zero, just set it up so it stops a few minutes past zero and then turn it the few minutes it takes to zero.
I put one on my Grendel with a NF 20moa mount and had to order some extra shims to get mine to work out.