I have used Yellow Cabs almost exclusively for the past several years. I do get exposed to other companies when I get a cab from the cab stands at locations like Foothills Hospital.
I've enjoyed the condition of the cabs, the caliber of the cabs and the good conversations (on almost every topic) as we drive along.
During the heavy snowfalls and poor parking availability at locations like Foothills the cab presents a viable alternative to driving yourself (The Calgary Transit takes an hour or more, estimates of your costs to drive yourself are about $1/km, and parking is a pain and a significant expense.)
Getting a cab to your location thru the dispatcher is almost always less than 15 minutes.
Over the past 20 years I've had two late arrivals of cabs that I've ordered the night before. I didm't enjoy that, but if I could demonstrate a better track record for mu personal scheduled events I might be upset