We have had two experiences with taking a radio taxi in Cape Town for the purpose of avoiding the drink/drive risk. The first instance we booked a taxi for 6:40pm on a Saturday. We got a call on the cell phone at 6:40 am to say they were outside waiting. I pointed out the error and the rescheduled for 6:40 pm that night. The taxi didn't arrive until 7:10pm after several phone calls. The driver was grumpy and moaned about his 'poor pay' the whole way there.
The next time we booked the taxi to collect us at 7:20pm and for a party we were going to at 7:30. No taxi, so we called at 7:40 to be told "we're very busy tonight" which is why I said we had booked the taxi a day before to avoid this, he said it didn't matter, but the driver would be there in 10 mins. Still no taxi by 8pm so we took our own car, and phoned to cancel the taxi and also the return taxi we had booked for 10:30 that night.
Sure enough the taxi we didn't need arrived at the party at 10:30 and was rightly upset that no one from the HQ had told him it was cancelled. Not great considering the need for reliable taxi services to combat the drink driving issue.