Booked via the Internet in Australia and the company were always in contact via email, confirming the pick up address, the forecast for the weather and possible alternatives if the weather turned nasty (which it did not).
They turned up on time. The driver was courteous and had a great sense of humour, taking into account that this was a birthday present to my wife. Having someone drive us around the Arc de Trimophe was an experience!.
If you want to see the sights in Paris and not share them with a bus load of tourists, this is the way to go.