I am convinced that this is the best cab company in the valley. I have now used them twice. They are the only cab company who advertises in the yellow pages that you can book them in advance, which is perfect for when I am feeling especially anal about my travel going smoothly around the holidays. Both times they have been early to pick me and Hubby up, and they take--are you sitting down?-- the shortest route to the airport from my house, unlike the bastards you usually get stuck with who will take a leisurely tour before they get my ass where it needs to go.
Union Cab's cars are clean and the drivers are friendly. I did dock them a star because this last time I booked online, but after several hours had not received a confirmation phone call or e-mail. I then called, and it was clear they had not gotten my order. So, just call instead, and rest assured that you will be on time, driven by a nice person who will not screw you over.
UPDATE: We used Union Cab a third time at Christmas- they were still early (and this was at 4:30 am!), still friendly, and still reasonable. Somebody got a big fat tip.