I've used this service a fair bit, and have also used quite a few of the other similar or related services like Royal Airport Conciege, the in-house one at Heathrow, Blacklane while it was operating (which was *great* by the way, sad they didn't make it), Global Airport Concierge, and a few airline ones like Lufthansa's service.

They can all be very hit or miss in terms of delivering value, in my experience the whole thing ends up depending mostly on if the airport is a complete mess when you get there. If it is, and lines are long, or something is going wrong, they are absolutely invaluable and worth every penny. Sometimes things were going to go fine either way, so it ends up being not a great use of money, or even a little distracting. It also depends on the rep you get. They are usually moonlighting airport employees so in a few cases I have gotten people who are like local airport gurus, for example the Blacklane rep at JFK who was the head of security and just walked us through various unmarked doors in an incredible shortcut to exactly where we were going. Sometimes they aren't assertive enough which is annoying.

Anyways, to respond to this actual topic. I've used Signature service at EWR a few times and it's been uniformly great. In each case it's been a former/moonlighting UA employee with a badge who has met us at the car, dealt with our luggage and taken it to be checked and come back with tags, walked us to the head of security and then gone into the United Club and found us a good spot to site, and even ran an errand to a local store outside the club to get something for my infant son. Pricing is very fair compared to the other similar services and I'd recommend it.