What the post doesn't mention: how many taxis they have signed up. This is important. Their launch of UberTAXI in New York was a failure for many reasons, but one was that no-one could ever get a ride, because it turned out they had barely any cab drivers signed up to use the system.
If they aren't mentioning numbers out of the gate then I'm skeptical. Also amused that this story is currently 3rd from top on the home page, but numerous stories about their utter failure in New York were nowhere to be seen on HN.