Depends on the company. Mail to the CEO is a well known customer support escalation path.
For companies that do generally support their customers, usually it gets you into an 'executive support' queue with people who are empowered to understand and solve problems that are mostly solvable --- you should be able to get money things made right, but don't expect product changes (but it can happen).
For companies that don't support their customers, it gets overwhelmed and may get dumped into the same usual support channels where reps aren't empowered to get anything done.
For companies that do generally support their customers, usually it gets you into an 'executive support' queue with people who are empowered to understand and solve problems that are mostly solvable --- you should be able to get money things made right, but don't expect product changes (but it can happen).
For companies that don't support their customers, it gets overwhelmed and may get dumped into the same usual support channels where reps aren't empowered to get anything done.