i went this morning before work (i have the luxury of going by on a weekend and watching or, as sunset is later in the day, going on my way home from work). watched for a few minutes.
its incredible to see them gliding silently, some with sticks (not twigs...actual branches) in their mouths, going up to their nest.
going at dusk is incredible because you see these huge, dark silouettes flying around. very Jurassic Park like.