I think they are still useful for countering arguments by the gun grabbers that CCW will lead to rampant increases in gun violence. After all, look at the wistful headline for the story from the Slimes:
More Guns in Citizens' Hands Can Worsen Crime, Study Says
They lead off with this aspect of the study, even though it is by far the weakest of Donohue's premises. So we still need factual information to counter the slop spewed out by the Brady Center, because too many swing voters, frankly, don't understand the underlying prinicples of limited government and enumerated rights.
I agree, but we also need to be careful not to overreach, which is what I think Lott did. I think he went to far in saying that CCW reduces crime. He should have been more careful about his inferences, particularly because even without the benefit of the 1993-1999 data his results were not robust. He should have instead have said, "I can say with confidence that CCW doesn't affect crime very much, and the evidence seems to suggest that it might reduce it, though this second finding is not very robust."