I'd just like to say that caching support kicks ass. My site (http://www.wii-linux.com/) was slashdotted and dugg at the same time yesterday, peaking at around 18,000 pageviews. The server is a dedicated single processor xeon running apache2/mysql on ubuntu breezy badger server with no special tweaks for speed. I had the cache set to 15mins, and throttled some of the more processor intensive stuff and there was only a slight slowdown in usability overall. If anyone is questioning the efficiency of Drupal's caching support, I'd just like to say it works great. :)

Drupal version: Drupal 4.7.x