Saw it in IMAX. Fully agree with your review.
I commented to my friend when we left that I was glad it was only an hour and forty minutes because I didn't know if my stress levels could take much more. It puts you on a tense edge from its first moments, and you stay there through the entire film.
And sandwich is dead-on about the score. The film is an assault - in the best way possible - on the visual and auditory senses. The minimal dialogue is key, because it leaves room for the soaring score that keeps you literally on the edge of your seat through the whole movie (and hey, I studied history, I know how it ended before I went in). The music makes this film and it is a masterpiece because you don't even realize you're listening to it until it ends. It's phenomenally well-done.
This is a historical movie, however - do not go in expecting a plot-heavy worm's-eye-view common to war films like "Saving Private Ryan" and series like "Band of Brothers." That doesn't mean it isn't just as good - it is - but its a sprawling review of what happened at Dunkirk rather than a narrow plot on one group. It's narratively, not character, driven - which may seem a bit odd, given than the events of the film follow three people.
This is a film that I'd say must be seen in theatre to be fully experienced, and I'd highly recommend the IMAX.