Why wouldn't hook_form_submit be called?
The form should be:

   function  mymod_reviewer_node_form($form_state) {
     $form = array();

     // Build the form...

     return $form;
   }


The submit handler should be:

   function mymod_reviewer_node_form_submit($form, &amp;$form_state) {
     // Do something with $form_state['values'] or whatever
   }


And make sure that whatever is rendering the form passes through drupal_get_form().

Finally, one tricky bit: Make sure you are not accidentally overriding a hook. mymod_form(), for example, implements hook_form(), which is probably not what you really intend to do.

I find that nine times out of ten, if the submit handler is not being called, it's because I named the function incorrectly.