That is exactly right. I always use this to send the user's browser to a path with all of the search terms in the URL. For example, search.module sends people to .../type/search+query. The following request will be a GET.
Then a page can be served in the usual way, not needing to worry about $_POST. arg(n), hook_menu()'s callback arguments, and/or automatically passed callback arguments may be used.
And the resulting page is bookmark-able.
(or you can return either NULL or FALSE, I forget which, from formtest_submit() and turn off redirection and use $_POST wherever you need it)
NULL, so that $redirect will fail the isset test. Here is the code where it's tested (form.inc line 201): // Since we can only redirect to one page, only the last redirect will work $redirect = call_user_func_array($function, $args); if (isset($redirect)) { $goto = $redirect; }