I found shooting from a distance relatively easy as people didn't notice me as much because I wasn't right in their faces and because I was so far away, the people that did notice weren't quite sure whether I was pointing the camera at them or somewhere else.
As I was shooting from across the street, passers by and passing vehicles did obstruct my view intermittently but it wasn't too much of a problem as the weather was poor so there wasn't too many people about. I would imagine this would have been more of a problem if the street had been busier.
Using an aperture of f/2.8 I found it easier to single out my chosen subject and blur background and foreground to create separation. The long focal length also compressed the scene somewhat and narrowed the perspective which creates quite flat images.