Layperson here, but based on reading I'm a little more pessimistic. The incubation period can be up to 21 days, and the subject can be infectious during that time [1]. Thus there is a plausible worst-case scenario where an undiagnosed carrier flies to a population centre and comes in contact with a lot of people.

Hopefully this could be prevented by contact tracing and other containment as described above, but if one carrier got out and infected people elsewhere, containment efforts might be unable to keep up.

1. http://ebola.emedtv.com/ebola/ebola-incubation-period.html