This reviewer (TJBNYC - host of one of my favourite sites: Stirred, Straight Up, With a Twist) at IMDB in 2001 puts it so well:
Susan (replacing Judy Garland) of course is in her element here as the "barracuda" stage legend and she has 4 great scenes, the initial one when Parkins goes to the theatre to get her signature on some documents (above) when Helen hears Neely sing and gets her fired from the show; "give me a fountain pen, not one of those lousy ball-points" Helen/Susan growls, in that red suit, and her line "I know all about run of the play conrtracts"! Later she sings that hilarious number "I'm going to plant my own tree", then there is the tussle with Neely (right) before her wig goes down the can: "listen, they drummed you out of hollywood so you come crawling back to Broadway, well Broadway doesn't go for booze and dope...", she then leaves without the wig: "I'll go out the way I came in", and her final scene when she admits Neely's talent but knows she will destroy herself .... Susan of course is heads and shoulders above the rest of the cast, though Sharon Tate again shows what a singular beauty she was.
The gay boys over at Datalounge.com (gay gossip site) actually have threads about Helen Lawson, a bulletproof Broadway legend, inventing various tv specials she did and things that went wrong with them as Helen boozes and cusses and causes havoc. Too, too funny .... Susan gives it her all here, really her last major movie, and Patty as Neely is dynamite too, and then there is Lee Grant stupendous as ever .... Trash has hardly been better, from the Jacqueline Susann best-seller (Jackie plays a tv reporter here), up there with Rona Jaffe's THE BEST OF EVERYTHING, another great Fox movie trash classic; or THE OPPOSITE SEX or WOMAN'S WORLD or those Lana Turner classics .... or Susan's BACK STREET, or those more luridly trashy HARLOW films and THE OSCAR and of course THE LOVE MACHINE from 1970, the acme of Trash from another Susann blockbuster, as per reviews at Trash label.