Drang: There is no question that the decision enjoins the DC police from preventing a non-resident from carrying is DC. However, keep this in mind. It took something like 6 years to get this decided. 6 years while two judges just sat on it until it had to be decided.
I'm not sure how long it would take the federal courts to free you after you are arrested for carrying in DC--probably not 6 years, but it could be many months. You'll "win" in the end, but DC's prison's are notoriously bad and notoriously unsafe.
There is, I think, around zero percent chance that the DC politicians will allow the DC cops to obey this decision, so I would recommend continuing to avoid DC for a while. Besides, Obama has recently remade the DC Circuit with some of the most left-wing judges ever nominated, and they are the ones who will hear the appeal of this decision. Don't be surprised if they reverse this decision on the grounds that guns are yucky and that women and children suffer when the 2nd amendment is honored. The Third Circuit recently upheld New Jersey's policy of only granting carry licenses to close relatives of politicians and made men in the mob (very often the same people) pretty much on the grounds that guns are yucky and that New Jersey has been violating the Constitution for so long that its now okay.