Not very. Songs are shown being performed in shows they were never part of, and in some cases years before they were actually written. Rogers and Hart went to Hollywood in 1930; Judy Garland, shown as an adult at the party there, was only a child at the time. It is true that Lorenz Hart was short, a heavy cigar smoker, and had major self-esteem and depression issues, but the movie also leaves out that he was an alcoholic and a closeted homosexual. (The lost love presented in the movie is a fiction.) Reportedly, Richard Rogers hated everything about the movie except the casting of Janet Leigh as his wife.

Basically, the movie gives a sketchy, highly fictionalized view of the Rogers & Hart partnership, leaves out many details of their characters, and is really more of an excuse to show some of the top stars of the day performing Rogers & Hart songs.