Reading the comments on this movie tells me a lot about our culture at the dawn of the 21st century. Yes, by today's standards this movie seems to move slow and a is little dull. It was made before pornography passing for entertainment was permitted. It contains lots of subtlety and innuendo. It was considered racy when it was made.
One of my favorite scenes is when Mrs. Eaton is talking to her husband on the phone about her lover. You never see the lover in the scene, but at the end, you realize he's been in the bed all along. Another favorite scene is when Mrs. Eaton meets her husband's lover for the first time. It is in the car afterward that she asks what this woman call's Mr. Eaton.
The only disappointment is the superficial way the film treats marriage. No children are involved in this marriage and it only deals with how the husband and wife consider their lives. It tries to make a case for divorce and treats the subject far too lightly.