Last watched this eight years ago. Back then, I wrote:
Another highly-regarded comedy, this time of the screwball variety, and, like many such movies, a favorite of mine. Irene Dunne apparently elicits mixed reactions from viewers, but I’ve always loved her in this movie. Cary Grant is Cary Grant, the Chow Yun-Fat of his day. The Awful Truth is less screwy than something like Bringing Up Baby, but that extra bit of grounding might actually help the film. Dunne and Grant play so well off of each other that you can watch The Awful Truth multiple times without the gags getting old. The gags are good, but the actors are even better. And the final scene, which is barely screwball at all, is witty and very sexy.
I wouldn't change any of that, although I'm no longer sure what I meant about Irene Dunne. I'm surprised I didn't mention a great, hammy performance by Skippy the Wire Fox Terrier. Skippy had quite the career ... even has his own Wikipedia page. Here he plays Mr. Smith, and he's even a key part of the plot. He's best remembered as Asta in some Thin Man movies, but he was also in Bringing Up Baby. He never got nominated for an Oscar, but The Awful Truth got six nominations, including Leo McCarey (who won Best Director), Best Picture, Dunne, Ralph Bellamy (his only nomination), Best Screenplay, and Best Editing. #414 on the They Shoot Pictures, Don't They list of the top 1000 films of all time. (It was #365 eight years ago.)