Page of Posts using multiple categories

Hello!

I’ve implemented the Page of Posts example from the Codex’s “Pages” page, and like it a great deal. However, I was wondering how can one make it so that multiple categories can show up, instead of just the one.

Here’s the code:

<?php
if (is_page() ) {
$category = get_post_meta($posts[0]->ID, 'category', true);
}
if ($category) {
  $cat = get_cat_ID($category);
  $paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
  $post_per_page = 4; // -1 shows all posts
  $do_not_show_stickies = 1; // 0 to show stickies
  $args=array(
    'category__in' => array($cat),
    'orderby' => 'date',
    'order' => 'DESC',
    'paged' => $paged,
    'posts_per_page' => $post_per_page,
    'caller_get_posts' => $do_not_show_stickies
  );
  $temp = $wp_query;  // assign orginal query to temp variable for later use
  $wp_query = null;
  $wp_query = new WP_Query($args);
  if( have_posts() ) :
		while ($wp_query->have_posts()) : $wp_query->the_post(); ?>

I’m thinking there’s probably a better way of doing it instead of using a custom field, and having very rudimentary php knowledge I’m not sure how to figure it out. I also don’t mind hard-coding the Categories if need be, as the cats are few and there won’t be many additions.

Any thoughts?