I agree with some of what Twisted says, and it is of no concern to me whether the driver has been waiting several hours - that's his choice. I'm certainly not going to carry the week's shopping to my house in this climate!
Generally, though, I think Dubai Transport offers a reasonable service. Not all the drivers are as safe or considerate to passengers as they should be, but that's another issue. Recently I needed to get to Media City in a hurry, so I ordered a taxi. It usually takes 5-10 minutes for one to show up, so when I was still waiting after 20 minutes, I called DT again. They could not find my booking on their system. This would mean that either a taxi had shown up and somebody else had taken it, or the booking was not input in the first place. Hmm. The operator ordered another taxi and said it would take 20 minutes. I protested that it should not take more than 5 minutes, pointing out that there are always at least a dozen cabs waiting just down the road at Ibn Battuta Mall. She told me there were no taxis in the area, and the nearest one was coming from The Lakes!
Well, twenty minutes is a bit optimistic to get from The Lakes to the Gardens, but I didn't have a choice. And I was right, the taxi actually arrived after 35 minutes. As we drove past IBM I counted the waiting taxis - 23 of the buggers. I phoned Dubai Transport again and spoke to the Assistant Operations Manager who apologised profusely and told me the system had been down and was not showing the taxi locations. I explained that I couldn't understand why a taxi at The Lakes had picked up the order when there were almost two dozen cars at Ibn Battuta.
Needless to say I was hideously late for my meeting, and bubbling with frustration when I finally arrived.