Some of the worst MK4's and VX-III LR I've had (all 6.5-20x50...been issued dozens of 10x, 4.5-14, 3.5-10, and MK5 with few problems):
One I sent in with a 10% error and they said nothing wrong with it.
One had 1/10th moa (not mils) adjustment and 1/4 moa turrets.
Sent one in that failed to hold zero (repeatedly), when I got it back you couldn't turn the windage turret by hand.
My .338 Edge wrecked one the first shot out of it, ended up sending that one back 3 times. 3rd time they sent me a new one, to which I sold.
That was the last one I personally owned, about 5 years ago. Since then I think they have been stepping up.
Also, their customer service has been great to deal with. They even sent me a loaner a week before a hunting trip because my scope crapped the bed.
Like I said, I'd really like to try a VX5HD. But you know what they say: fool me once shame on you, fool me a dozen times and shame on me.