I had a couple bad experiences with AV's, but was told the problem was solved by the time the Z3's came out by different assembly methods, despite the erector-spring system being basically the same.
It's only a sample of one, but I've had a Z3 3-9x36 for several years now. It's been on at least half a dozen rifles, including a Weatherby Mark V Ultra Lightweight in 7mm Weatherby Magnum, and had functioned perfectly on each rifle.
