I booked Bell Trans for our airport to strip hotel shuttle needs on our last weekend trip to Vegas. The booking was easy enough through Expedia and the pricing easily beat everyone else.
The reservation process to use the voucher for the return trip is to call in 24 hours before the time you need them to arrive. The process is an automated system so you will have to stay on the phone for a while to listen through all the prompts and type in all the information on your keypad.
The pick up driver was 20 minutes late which is why I knocked off a star. I had to call in about 10 minutes after the hour in which we were suppose to be picked up at the hotel to get to the airport and they had to radio the driver to figure out where he was. I suggest everyone to give yourself plenty of time when going to the airport in case this happens to you as well.