--opt is a shorthand for the combination of several options. Note that after saying --skip-opt, he proceeds to add most of the options that he just turned off. The two missing ones have to do with locks. A guess: mysqldump (and --opt) was probably invented back when there was only MyISAM. Table locks were (are) advisable for that engine. With InnoDB, --single-transaction is probably a better option for InnoDB; is he assuming InnoDB only?
Does any of this matter? If you have a small system and no one is modifying the data during the mysqldump, then no.
If you have a huge database, --extended-insert can easily speed up the reload by 10x.
If you might have concurrent INSERTs/UPDATEs/etc, then some form of locking is strongly advised, else you could get an inconsistent dump.
See the discussion of --lock-tables in
http://dev.mysql.com/doc/refman/4.1/en/mysqldump.html
See also --lock-all-tables
For a huge table, --quick (a misnomer) is essential.
Read the discussion about --single-transaction if you have a mixture of InnoDB and MyISAM tables.
I prefer to stop mysqld, copy all the files, then restart mysqld.