Quite simply: I love this movie.
Clark Gable, Myrna Loy and Jean Harlow give wonderful performances as participants in a love triangle that never really gets off the ground. That's actually one of my favorite things about this movie (the fact that Whitey and Van never become romantically involved). It's easy to see that there is an attraction there, but I think the fact that they never become involved makes this a better movie.
It would have been so easy to write this as the stereotypical man-has-affair-with-secretary movie and to make the character of Whitey the stereotypical man hunting secretary. It was especially refreshing to see Jean Harlow play such an understated and intelligent role. The character of Whitey also has a heart and this is shown perfectly when she tells Linda to go back to Van or she (Whitey) won't turn him away when he turns to her.
Gable played the role of Van perfectly. It's obvious that Van is head over heels in love with his wife yet (most notably in the Havana motel room scene) you can also see that he's fighting an attraction to Whitey. I don't think that attraction to Whitey would ever have won out over his devotion to Linda, but it was obvious he would turn to Whitey when Linda filed for divorce.
Myrna Loy gave a solid (if one note) performance as Linda. (That's not her fault, though, it's how the character was written.) I'm not sure how it could have been done, but this movie would have been even better if Loy had been given even better material.
The costumes and set decorations in this movie were top notch. Both Loy and Harlow wore stunning costumes that were always appropriate to their character (Loy the wife of a wealthy businessman and Harlow the lower class secretary). The apartment of Van and Linda was impeccably furnished and I especially loved the touch of having windows by the upper portion of the curved staircase.
On a completely shallow note, the party scene where Gable dances with both Loy and Harlow is my favorite scene in the movie. He's so smooth, so effortless and so dashing on the dance floor. I was definitely born a generation too late.