There's been a lot written lately about DC's declining murder rate and crime stats in the general, and Columbia Heights follows a similar trend, though not exactly the same.
Using the data from crimemap.dc.gov, overall crime in Columbia Heights (that is, within a 1500 foot radius of 14th and Irving, which goes from about 17th to 11th, Newton to Fairmont) dropped 3% from this year (1/13/09-1/13/10), versus the past year (1/13/08-1/13/09). Total violent crime dropped 14%, though assault with a deadly weapon with gun more than doubled, from 7 incidents to 16. Homicide doubled from 2 to 4. The chart is on the right, click it for a bigger one.
For the entire Third District, which includes all of Columbia Heights up to Spring Road, Mt. Pleasant, Adams Morgan, Logan Circle, Pleasant Plains, Howard U, and part of Shaw (map here), crime has dropped 5%, with homicides down 30% (23 to 16) and violent crime down 8%.