I actually saw this movie by chance... A friend of mine saw the VHS on a shelf, tucked away in the back of Cinema 1. She pointed it out, and I bought it immediately.
The storyline itself isn't realistic; very rarely would this happen in real life (if ever), but it's touching, funny and brilliantly acted. Alda and Burnette have incredibly great chemistry on-screen. It's a laugh a minute with those two. The characters are so finely drawn with their own little quirks and personalities that it's easy to believe they're real.
The film also shows just how easy it is for something so seemingly trivial can threaten a friendship--- In this case, it was the addition of Ginny.
The seasons seem to perfectly follow the character's moods. During the spring and summer, the atmosphere is pleasant and carefree; nothing can go wrong, the sky is the limit. And as the weather turns colder, the moods follow suit, reaching the `coldest' point during the winter, where their true colours begin to show.
Oddly enough, though I bought the movie to see Alan Alda, Anne Callan (played by Sandy Dennis), turned out to be the highlight of the film for me. In contrast to the ditzy and annoying Ginny, Anne is incredibly witty, albeit a little off-beat and *out there*. She has some hilarious lines, and Dennis delivers them perfectly-"The hell with Nick. Tell him it's a goddamn boa constrictor!" And her wacky memory (for example, remembering the day she got her tooth filled)- Too funny.
Whether or not you're a fan of any of the actors or actresses in this movie, I highly recommend it. You'll fall in love with it.