I have several on multiple scopes and they are great. So far, I've shot out to 600 on all guns and the clicks are on. Also, if you have custom data, he can do a BDC with your data.
Another nice trick: Zeiss will retro-fit your scope with standard knobs and replace them with target knobs for $50 each. With a target knob, you can add a Kenton BDC. So, for a sample list Conquest 3-9 for $350, you can add an elevation target knob for $50 more and for another $70 have a trajectory-specific BDC. So, for less than $500, a "no more confusion" scope: range the target, dial in the range on the BDC, hold on target, squeeze. And it really helps with those scopes like Zeiss where the damn knobs are bass ackwards!!