Originally Posted by
moondog
1) "Unofficially", they can and will tell you to pound sand if they don't care for your destination. (This was not true ~10 years ago before McDonalds employees surpassed them in the income category.)
2) Advance bookings are okay during off peak times, but good luck pulling one off during an afternoon in the CBD.
True, it depends a lot on the taxi company. The company I find that has the best overall service and cleanest/newest cars is 首汽 Shou Qi, but especially in the East of the city it's hard to find empty 首汽 cars around. All the taxi company names are printed on the outside of the cars though, so if ever you have the choice you can opt for them.
Advance bookings are useless at certain times and places though, it is most useful if your calling a cab at 2AM and don't want to be standing out on the street for 20 minutes or if you're booking ahead for the next day.