I see ADS-B transmissions daily and it does concern me the inaccuracies which can occur compared to ground-based radar systems.
If you watch a "radar" picture of ADS-B equipped aircraft flying into Heathrow, for example, you'll see that the odd one "lands" in Windsor Great Park, or Wimbledon High Street. If the accuracy needed by ATC is to be determined by crews setting up their ADS-B equipment correctly I think the integrity is in doubt. If someone squawks the wrong code it can easily be picked up... but how does one know that an ADS-B location is true?
Hopefully someone can put me right.