I thought it was very well filmed with many exciting shots that did not over dramatize depicted events, but reinforced the emotions of those moments. The acting was superb all the way around. There is some fictionalization mingled in (particularly in the personal scenes surrounding the war), but the historical facts seem mostly correct. I doubt Churchill privately suffered over the decision as much or in the way it was depicted, but the audience seemed gripped by it all, so I would say all of that was very effective. Oldman took center stage in this movie in much the same way George C. Scott did in Patton, and the viewer comes away with positive feelings of both men when those movies end.
On another subject, smoking was cut to a minimum even though the events take place in 1940. There was a pipe in an ashtray at a table, but there wasn't one smoked, and mostly, only Gary Oldman as "Winston Churchill" was smoking. Two people smoked a cigarette. At the end of the movie was a disclaimer regarding second hand smoke and that the movie did not encourage smoking.
