I like BBCLONE's visitor statistics package. It has served us well for more than a few years. Our customers like it too. There is a problem though. Drupal and BBClone do not get along very well. Here are a couple of tips to get BBClone working with virtual hosts (multiple sites hosted via one single drupal installation), and with caching enabled.
Most of the helpful hints proposed on http://drupal.org/ suggest installing the relevant BBClone code in the ~drupal/index.php file, like so:
$bbrequest = strtolower($_SERVER["REQUEST_URI"]);
if (is_readable(COUNTER)) include_once(COUNTER);
This is all fine and good, but if you are hosting multiple sites under ~drupal/sites/ then you are going to have a problem. Each virtual site has its own statistics counter and bbclone directory. We want each site to count only its own vistors.