<?php
  $id_array = array(589,98,1021,531);
  $args = array(
     'post__in' => $id_array,
     'caller_get_posts' => 1,  // stickies will mess this up
  );
  query_posts($args);
  if (have_posts()) {
     $id_ndx = array();
     $orig_posts = $wp_query->posts;
     // Create an array of IDs and their index number.
     for ($i=0;$i < sizeof($orig_posts) ;++$i ) {
        $id_ndx[$orig_posts[$i]->ID] = $i;
     }
     $wp_query->posts = array();
     // Rebuild the $wp_query->posts array in the order of $id_array
     foreach ($id_array as $id) {
        if (isset($id_ndx[$id])) $wp_query->posts[] = $orig_posts[$id_ndx[$id]];
     }
     while (have_posts()) {
        the_post();
        echo "<p>ID: $post->ID</p>";
     }
  }
?>