I have used the service quite a few times for both transfers and arrival/departure.

For transfers it is quite useful if you arrive on a flight with security re-screening. If you travel in economy you get to use the fastlane at security and the staff usually makes sure that you are being prioritized. The staff then takes you to the "correct" lounge, the one that you are currently allowed to enter, which can vary .

For arrivals it is quite nice as you can wait in a lounge until your visa is being processed. They are usually well prepared and guide you through the formalities and wait times are very short.

For departures this is probably the nicest experience. The times that I have used it, I was pretty much the only one in the lounge and security was a breeze i.e. I was the only person going through.

I usually email them two or three weeks in advance and I get a reply within a few hours confirming the service.

I only once got an email stating due to high seasonal volume they would not be able to confirm/offer the service. A day or two later I got a follow up email saying that they are now able to accommodate me.

All in all a nice complimentary service.