Been in place in SA for 6 months, and in WA for more than a year.
Biggest problem was/is people were getting pulled over and fined because the rego dept computers were not updating the police computers fast enough. There was about 4 week lag, the cops wouldn't call rego dept. so you had to get the receipt (if you didn't have it in the car with you) and produce it at the court to get the fine removed.