What benefits and demerits do External Style Sheets have?

Benefits:
One file can be used to control multiple documents having different styles.
Multiple HTML elements can have many documents, which can have classes.
To group styles in composite situations, methods as selector and grouping are used.
Demerits:
Extra download is needed to import documents having style information.
To render the document, the external style sheet should be loaded.
Not practical for small style definitions.