For those who may not have noticed it, it looks like Drupal 7 is going to require not only PHP 5.2, but MySQL 5.0 as well. It makes sense to do. Drupal 7 won't actually ship for another year, by which point MySQL 4.1 will be on life support anyway. It will also lose all support during the Drupal 7 life cycle. So if you're planning a new server, get ahead of the curve and Go MySQL 5! :-)
Drupal 7: The version that gets over the 20th century.