This was a good service, although, there was a long wait to get the bus upon arrival. It may have been better to pick up a bus as you arrived. I noticed no difference in terms of getting a bus having the reservation or not.
We sailed through immigration unheard of! at Newark, but had to wait 30 mins for pick up, they put down a time ahead of when you meet them to make it look as if the delay was less! We then drove to wait at another terminal before finally setting off. The driver then took an extremely long route into Manhattan, a 30 minute journey taking us 2 hours. I have used this service from JFK and it was much better. It's probably just luck.
This is a great service if your happy to wait 20-30 min after your flight - The Driver was helpful getting bags in and out of car - great service for the price would use them again