Before this film, I had seen Susan Strasberg in two late 1960s AIP low-budget films 'The Trip' and 'Psych-Out' and enjoyed her performances in both so was quite interested in seeing her in the starring role here.
Alas, not only is she not up to the task, but she takes down the film with her. Her performance in the first 30 minutes or so is truly wretched; she's so strained and overwrought that it makes one cringe.
To be fair, from the time she does a reading from 'Romeo & Juliet' (which is quite charming) her performance settles down somewhat but the damage is done. After all, it's in the opening scenes where we're supposed to believe that she wins over Herbert Marshall as a close friend and enchants Plummer and Fonda but her performance kills any chance of that being convincing and the film never recovers.
However, the film is still fairly entertaining. While Fonda seems rather too genial to convince as a Broadway producer he's always entertaining to watch and helps hold the film together. And Joan Greenwood does a nice balancing act as she gives a melodramatic performance yet still lined with depth.
And, as other reviewers have mentioned, director Sidney Lumet puts in some nice touches with the detail he displays in the preparation that goes behind the scenes for opening night.
Also of interest is that it was released as an RKO picture and was probably close to the very last film released by that studio.