The vintage Necchis are very good machines and here in the states tend to command higher prices than other machines. Mostly, they're worth it. They are built to tight tolerances and most attic fresh machines(or just any that haven't been used for years) tend to be real stiff or frozen up. They're worth the time to unfreeze them. The Yahoo group has a great cleaning/unfreezing tutorial. Some of the later Supernovas have a nylon worm gear in the top that's a bummer because if it breaks there aren't replacements. Some members of the Yahoo group have talked about having it 3D printed but it hasn't been done yet that I know of.They also have a fragile needle clamp assembly that if it's broken, there's no fix for it. The only other model to watch out for is the Lydia. It's famous for having a cracked cam stack. The other models, the BU, BF, BC, Mira, Nora, Nova, Lelia, are great machines. The Supernovas are too if you get one with the metal worm gear.
Cari