I live in downtown Atlanta and Uber is huge among the intown population. I know people who have sold their cars solely because Uber X was introduced. Perhaps intown Atlanta is in a similar position to SF of density and lack of transit. Cabs here are simply awful. They don't take cards, you're lucky if one will show up within an hour (And I live one block from the central subway station), and they a guaranteed to try and rip you off somehow. Uber arrives in minutes, is cheaper, and the drivers are friendly. I was shopping for a car until Uber X arrived, but now uber fills the gaps in our public transit system.

As more and more young people are moving into the cities again, especially cities in the sunbelt that lack the public transit and availability of cabs of NY/Chicago, there's huge opportunity for uber. When you consider all the people now moving back into downtowns and wanting to live the urban walkable lifestyle, but in cities with subpar transit, the opportunity is massive.