I have a 6x6 Nettar with the Novar f6.8 lens. It is a great camera, pocketable and capable of producing prints that put ordinary 35mm shots to shame. It also has a 'cute' non-threatening look to it so people don't pay much attention to it -- unless they are fellow photographers.
5x7 prints of shots made wide-open are perfectly acceptable, I wouldn't go looking at the prints with a 20x loupe though. At f11-16 it is good enough for most any purposes, but don't expect to compete with a Hassy. Lens to lens variation may be significant, but this is just a WAG. They also made the camera with an f4.5 Novar, I don't know how well this performs wide open. A good triplet is capable of excellent performance, the problem is that a good 4-element Tessar is cheaper to make than a good triplet because triplet tolerances are very tight for optimum performance. Most triplets are made for low cost - so getting a good one can have an element of luck to it.
I would try to get one with an up-market shutter. I find the base Vario with 25/75/200 speeds is a bit limiting.
As already mentioned, it is a good idea to check focus alignment, as it is on any folding camera (and on _any_ used [even new] camera). Scotch magic tape stretched across the film gate makes a good focusing surface. Pick an infinity target. At wide open check the image center's sharpest point is with the lens focused at infinity, and that the corners are equally fuzzy. You can also use a closer object and use a tape measure to set the distance from the subject to the film plane. To check focus I place several screws head down on a table, in a line at a 45 degree angle to the camera, spaced an inch apart. I set the distance for the middle screw and take the picture wide open at the closest focusing distance. I then check the resulting photos and make sure middle screw is in focus and that the sharp focus range is roughly the same forward and back.
