Pauline Kael
“It's no surprise that Keaton and Lange are full-scale funnywomen; the news here is that Spacek, after all the tiresome studied acting she has been doing in recent years . . . can still play on instinct and be terrific . . . . She has real voltage here; she holds her own with big Jess and gurgly, wild-eyed Keaton--and with energy to spare….
“Keaton's Lenny is abashed about everything; she has so many timidities she's in a constant tizzy. Keaton is a master of high-strung unsureness; when she plays comedy, she has a miraculous gift for fumbling in character--for showing you the emotional processes that lead the character to say what she does. What makes Warren Beatty's performance in McCabe & Mrs. Miller stay in the mind in a way his other performances don't (not even his Clyde Barrow) is that he shows you McCabe fighting through his own clumsiness and confusion, trying to express what he doesn't fully understand. That's whay Keaton's Lenny does. Her tangled feelings spill out in all directions, and what makes her a great comic presence is that she always reveals more than she means to. Babe and Meg talk about how she has been turning into Old Grandmama--Lenny wears her grandmama's sun hat and gardening gloves, and she huddles, and hides her body in shapeless pinafores. (In some ways, the play, which was first performed in 1979, is Beth Henley riding the 1977 Annie Hall down South.) Keaton's nervous old-maid Lenny is a much richer character than you could guess from reading the play. She's a wonderful mixture of raw shyness and unconscious, eye-batting flirtatiousness, and her "fumbling" lifts the character right off the page. Even her feeling her way into a Southern accent seems to become part of the character. And Keaton is great at playing a sense of injustice for laughs: Lenny's resentment of Meg for having been granted childhood privileges denied to the two others wells up in her uncontrollably, as if she were still thirteen. She's had so few experiences as a grownup that she keeps their childhool alive all through the movie. She's the responsible sister--a thirty-year-old hopelessly good little girl longing to be naughty.

Pauline Kael
New Yorker, December 29, 1986
Hooked, pp. 233-237