Actually, the play's ending is quite different, although they don't end up together. In the play's ending, they meet at the bridge, and that's where he gilts her, accidentally pushing her off the bridge. The actual ending of the movie, with the flower children, isn't very successful, but the point remains that she is optimistic despite the difficulties of her life. It's quite similar to Gone with the Wind.
I think Shirley MacLaine is tremendously effective in this movie. If you watch the scenes and skip the very effective dances, Shirley gives an Oscar-winning-calibre acting performance. Just watch two scenes: when she's conversing with Montalban and when she's breaking up with John McMartin. Her character is very successfully developed as a mixture of brightness and undereducation, shyness and gregariousness, pathos and strength. Her phone call back to her friends (after the breakup) is a paragon of good acting. I wish she hadn't always worn those false eyelashes, but I suppose that was what normal women wore in the 60s... but they hide her eyes, a lot of the time (on my big screen).
This movie was overlooked because when it opened, its style was already dated (it seems more like 1965 than 1969). Now, of course, it out-60's Austin Powers -- the costumes in particular seem hilariously right-on.
Bob Fosse alone among Broadway choreographers knew how to use the camera (his early career was in Hollywood musicals like Kiss Me Kate). Note the deep focus which really livens up his original choreography for "Big Spender." And he makes sly allusions to that other New York musical of the 60s: West Side Story. The number "There's Gotta Be Something Better Than This" is a Latin-flavored dance very reminiscent of "America" from WSS. Fosse sets it on a rooftop! like the original, and there is the original Anita from the Broadway show, Chita Rivera, to help the audience connect to the parody. In another allusion, after the "Rich Man's Frug," Montalban asks Charity to join him on the dance floor. She quietly walks up, and the music cue is an unmistakable pickup from "Dance at the Gym" from WSS, as if she is Maria and he is Tony. They slowly come together while other dancers are frenetic around them, and then Charity steps on his foot. Parody ends with a hilarious punchline.
There are some sound problems on my DVD, but otherwise, I'm absolutely thrilled to have this. But why no commentary? Certainly Shirley herself is available, and so is Chita and John McMartin. Fosse and Verdon are sadly, gone.
One more thing: having not seen this movie for 15 years, I was quite surprised how much Renee Zellweger (in Chicago) reminds me of Shirley MacLaine, in her mannerisms and even looks.