One of the markers used to target the final run was my old station at RAF Laarbruch http://en.wikipedia.org/wiki/RAF_Laarbruch
The military value may have been minimal, the raid only put back work for a few months, but the big impact was on German morale'.
Goerring stated "No enemy aircraft shall fly over German soil," and yet here were heavy bombers deep in German territory. The once arrogant, Teutonic pride was visibly shaken. If bombers could do this, imagine what fighters could do.