She used her clout at Columbia management to kill more than one career of promising young Australian sopranos. She was THE diva and was not about to have any competition from "the next Joan Sutherland" as they used to call these aspiring singers.
On an artistic level, she sang exactly as she was: cold and incomprehensible. You could say she put opera on a popular level in the united states when she sang her famous "mad scene" from Lucia for the television in the early 60's. This was the real beginning of her long career. She certainly had the vocal technique to last as long as did on the stage. But in the end, that's all she left to posterity. At least, that's MY opinion.