It helps a great deal.. well.. maybe not. It helps in locating the specific target such as GVs, but not very necessary against area targets like cluster of buildings.
The trick to using this, i have found, is to have the default "forward" view showing the DB sight, and the alternative "forward" view showing the default view you have when you first flythe VAL(in short, switch those two).
With this, dive bombing soon becomes a joy