The technical support web sites of Nikon USA and Nikon Europe have both published somewhat ambiguous statements addressing the issue of "banding", or vertical line artifacts, in D200 images.
The statements acknowledge that "a limited number of early-production" D200 cameras may show excessive banding under some conditions. Nikon says it will adjust affected cameras free of charge.
The much more detailed statement on the Nikon USA site makes a distinction between "long banding" and "short banding". This statement promises that what it calls long banding will be adjusted under warranty but does not directly state whether Nikon considers so-called short banding a defect that it can or will fix.
It also does not make any direct statements about what can be expected from newer production D200 cameras or how to identify them, if you are a prospective D200 buyer.