The taxi turned up early, which was great. My only qualm is that the driver charged us an extra 20 dollars for tips and tolls. I didn't see us going through any tolls, so I was surprised that we had to give him 20 dollars extra. If I used them again, I would check exactly at the time of booking what extra money should be given to the driver. Apart from that it was a great service, but do remember to ring up the day before your departure to confirm your booking.
The driver arrived early so we could get to the airport quickly. A great trip to JFK from our hotel.
In New York it may be best to not say that they driver will be 15 mins, when in fact traffic does not allow 15 mins - both booked cars were late