And taking this into account, the film actually managed to do quite well come Oscar time, winning 4 awards (including one for Jason Robards' supporting performance and William Goldman's screenplay).
That said, Gordon Willis' cinematography wasn't even nominated.
Awesome Music: David Shire's score is one of his best. It's so quiet that it's almost subliminal, but if you listen it starts out with a strong noir flavour as if to emphasise the ubiquitous corruption, and as the reporters get closer and closer to the truth, it changes slowly and subtly into an equally quiet Theme Music Power-Up, without ever getting obtrusive. When we first hear the music, it sounds almost like the theme from The Twilight Zone, fitting with the bizarre events to come.
Genius Bonus: It's certainly not a requirement for enjoying the movie, but having a working knowledge of Watergate and the Nixon Administration (which contemporary audiences definitely would have) will make it easier to navigate the massive barrage of names, dates and figures mentioned throughout the movie.
One-Scene Wonder: Hal Holbrook as Deep Throat only appears in three scenes of the film, but his menacing, cynical performance casts a shadow over the entire rest of the film and his performance was so iconic that arguably every example of the Mysterious Informant trope since has been influenced if not directly inspired by him.