The online cab ordering/payment system makes calling a cab such a breeze. You can order in advanced (at least one hour ahead of time), or you can ask for a cab to be sent as soon as one is available. The online system also allows you to track your cab (once it has been assigned to you) and gives you an estimated time of arrival (fabulous!).
Side note: I noticed that calling the number they have listed on their website is a huge pain in the ass and the hold time is always longer than their estimate. As such, I really appreciate the new ordering system because it allows me to bypass the wait time on the phone and to avoid speaking to operators who sometimes have trouble understanding what I am asking for.
When the cab arrives at your address, a text is sent to your phone and you are able to communicate with the driver via text (in case of delay/change of plans, etc.).
Also, since you enter your credit card number into the online ordering system, once you get to your destination and are ready to 'pay' for the ride, all you have to do is sign a piece of paper and write in the amount of tip you want to leave, and everything is set. There is no need to pull out your wallet and risk leaving it in the cab or dropping it on the street!
Thumbs up, Union Cab! I'm in love with all this technology!!
PS. If you get cab #59, you are in for a treat. The driver is a real sweetheart and a great conversationalist. Ask him for advice on which airlines to take and you'll get a lot of good tips and tricks. :)