I do a lot of business in SY.
I will NEVER use a cab in Sydney. Over the years, I have had so many negative experiances with this group of thieves.
I can recall a single good experiance ex-SY airport. It stands out clearly as this particular driver had a spotless car, a smile and did not try and rip me off by already having the meter running at the stand, taking the wrong exits, being surly and aggresive when given directions and adding a random $5-$15 on top of the meter as being 'Airport Fees'.
Even if I am in SY for a half-day, I will use a rental car (with Sat Nav!). It often works out a similar price but without the stress and agro.
I have also experianced Ratbag cabbies in BN, ML and PT - but overall, these cities have much better Taxi standards.