Notices on the front-end

You could filter the_content:

add_action( 'post_updated', 'wpse105892_add_message', 10 );
function wpse105892_add_message() {
    add_filter( 'the_content', 'wpse105892_display_message' );
}

function wpse105892_display_message( $content ) {
    // remove the action once it's run
    remove_action( 'post_updated', 'wpse105892_add_message', 11 );

    $content = "<div class="your-message">You did it!</div>\n\n" . $content;
    return $content;
}