[development] replacing hook_user('form') with hook_form_alter()

hook_user('form') should probably be deprecated in favor of simple hook_form_alter() implementations. one wrinkle though is that hook_user('form') returns its fields in 'categories' which map to different tabs when editing a profile. do people think this multiple tab model is useful? if so, can modules achieve this in some way without help from user.module? Any ideas on how to improve this? -moshe