You need to understand what a Shepherd scope is and what it isn't. Don't worry about the one-shot zero stuff. You can zero the scope in a conventional manner if you prefer and it's really a secondary issue.
The Shepherd is NOT an X-ring scope. If you're looking for high scores on conventional bullseye targets in situations where you have time to twirl dials, look at something else. On the othe hand, if you want to put effective holes in multiple targets at multiple ranges, coupled with an auto-loading rifle, nothing else can stay with it. In contests where multiple steel targets are laid out at unknown distances, I've clanged every target with my SR-25 and have my mat rolled up and gear stored while all the guys with bolt guns and conventional scopes are still twirling dials, running bolts, and scratching their heads. But I ain't taking it to a Palma match.
The prior poster is also correct in that you need to determine whether or not your bullet/BC/MV combination will track one of the Shepherd BDC reticles. For instance, a 175 gr Sierra, parting company with the rfile right at 2,700 fps, in the climate I live in, will fly the P-2 reticle like it is wire-guided.
Luck,
SD