This is the conventional approach to stacking and velocity analysis. It is often satisfactory. Sometimes it is unsatisfactory because the dip angle is not a single-valued function of space. For example, near a fault plane there will be diffractions. They are a superposition of all dips, each usually being weaker than the reflections.
Many dips are present in the same place.
They blur the velocity estimate and the stack. Although migration is somewhat insensitive to velocity when only small angles are involved, migration becomes sensitive to velocity when wide angles are involved. The migration process should be thought of as being interwoven with the velocity estimation process. The moveout correction should be considered in two parts, one depending on offset, the NMO, and the other depending on dip. This latter process was conceptually new.