I have owned one and sold it. Your praise for this camera is well-deserved! I had mine for over a year, exposed maybe 20-30 rolls, and I did not have to replace the battery. However, the rangefinder had to be re-adjusted twice, and the procedure itself is quite delicate and not nearly as straightforward as a Leica. I damaged mine by putting too much pressure on the adjustment screw. Frank Marshman was the only person I could find who repairs them. He also happens to be the go-to expert for Plaubel Makinas, the closest alternative to the GF670.
Will I ever consider buying another one? I don't think so. Its fragility and price always made me feel a tiny bit anxious when I was using it. Not a pleasant feeling. But if I could afford 3 of them, i.e. one working and two spares, then sure!