For me, Good Night, and Good Luck fell squarely into the same genre as Downfall: an important movie, but not necessarily a good movie. It ticks a lot of boxes and zipped along at a fair pace but never really engaged me any better than a documentary on the same subject could have. In fact, the chapter about the Murrow/McCarthy feud in John S. Friedman's The Secret Histories did a better job of providing a context for the broadcasts than Clooney's film and remains, for me, more entertaining.
Although perhaps that's because I wasn't being forced to chew down some paper-thin character development for paper-thin characters. I don't know.