How many times have I got excited over a car and later discovered it was a replica... However, I'd probably feel a lot better about flogging a replica around a track. There's plenty of cars which are so accurate that it almost doesn't matter. Take for instance the DB4 Zagato Sanction II, Rosani's Lancia D24s or Fusi's BiMotor.
If we ever achieve good steel 3D printing, then the game will radically change:
3D printing - Wikipedia, the free encyclopedia