First of all, a comment on style. Atonement ticks all the boxes in Britishness. You cannot but love the mannerisms, the photography and the dialogue. A classy film only Brits can do.
Then, it's the acting. Although all performances are great, there are two performances that stand above the rest. James McAvoy and Saoirse Ronan. Sometimes characters define the actors, but these two actually redefined their characters. Keira is undoubtedly stunning and lovable and she did indeed great, but she's overshadowed by the sheer quality of the other two. From the other two Brionys, Vanessa Redgrave shows what an excellent actress she is by perfectly mimicking the posture, gestures and talk of little Saoirse, while Romola Garai unfortunately was not such a good fit (and it seems this is mainly a casting error).
Finally, the story is very well told and while the movie may leave a sad taste, it is actually a proof of its strength. This is what good movies do. They have the capability to imprint sentiments to the audience.
Then, it's the acting. Although all performances are great, there are two performances that stand above the rest. James McAvoy and Saoirse Ronan. Sometimes characters define the actors, but these two actually redefined their characters. Keira is undoubtedly stunning and lovable and she did indeed great, but she's overshadowed by the sheer quality of the other two. From the other two Brionys, Vanessa Redgrave shows what an excellent actress she is by perfectly mimicking the posture, gestures and talk of little Saoirse, while Romola Garai unfortunately was not such a good fit (and it seems this is mainly a casting error).
Finally, the story is very well told and while the movie may leave a sad taste, it is actually a proof of its strength. This is what good movies do. They have the capability to imprint sentiments to the audience.