I guess I'm giving it a 10 out of 10 for the acting, for the lighting, and for the attempt.
In other words this is a movie that you want to watch, a movie that will probably be enjoyed (unless you find movies like this boring, and, if you do, you've already made up your mind not to watch it).
However, it fails in the execution. Frost/Nixon should have been a struggle between minds, a chess game, and because of that it needed to have almost a paranoia to it. A tension that could be felt as one side attempted to take down the other.
It missed the opportunity there. Possibly because it was only an interview, possibly because the results of which didn't really matter, either way it missed the tension boat and the film ultimately suffers for it. What could have been All the President's Men turned into something well done, but ultimately forgettable for failure to really develop the mood to set the pace.
However, the acting was superb and the film certainly looks great. It is a pleasure to watch, it just never gets to the emotional level it needed to be brilliant and memorable.