For longer trips, a limo/hire car service is definitely the way to go. I get to see a lot of the hire car drivers around the airport and they take a good deal of pride in their uniforms and cars. They know what's what, they have years of experience, they are the First Class of the taxi world.
I guess with Silver Service, I'm Business Class. I aim to deliver my passengers safely, comfortably and cheerfully. Happy passenger = happy cabbie, in my book.
For regular taxis, it's a mixed bag. I hear a lot of horror stories of drivers who can't find Parliament House, who routinely go a longer way if they passenger is from out of town, who try to maximise the red lights, who won't help with the luggage, etc. etc.
And I know some of the regular cabbies are superb drivers, who love the job, have high standards, years of experience, a book full of loyal customers.
Bottom line, if you find a cabbie you like and trust, ask for his card and try to establish a relationship. He'll appreciate having regular customers - generally a friendship develops which makes trips pleasant for both - he'll get to know your preferences, he'll aim to make you happy.
Alternatively, if you are at a rank, you don't have to take the first car. It's good manners to do so, because that driver has been waiting longest, but not obligatory. My rule of thumb for picking a cab is to go for the cleanest. The driver will have higher standards than the rest.