How to redirect user to new page after submitting user register form?
The syntax that you use is not the same as in the API docs. The qis to much.

Also, you shouldn't manipulate $_GET, that's not at all reliable. The correct way to achieve what you want, is to add a custom form submit handler and when that is called to set $form_state['redirect'].

Have a look at the accepted answer to this question: https://stackoverflow.com/questions/14542975/drupal-7-redirect-to-a-specific-page-a-tab-after-form-submit