Here is a review I wrote for the 13CABS app on the Apple Apps Store:
After a bad experience last year waiting 3 hours and 15 cancelled taxi's, I had been using Silver Top until now. Found this app and thought I'd give them another go.
This morning, 2 taxis's decided to pick somone else up on the way to get me. So after 40 minutes waiting I called Silver Top who were there in less than 10 minutes.
ONLY USE THIS APP IF YOU DON'T REALLY EXPECT THE TAXI TO TURN UP.
Install the Silver Top Taxi App. Not as usable, but if it's a taxi you want, they are the ones to call.