SavannahNow is the web arm of the Savannah Morning News, a print newspaper in Savannah, Georgia (USA). It's built on a customized 4.6.8 platform. Some statistics:
For the rest of this year I'm using Drupal's book module for a substantial collaborative research document (250,000 words, 50 authors, 130 peer reviewers).
To make better use of the Drupal.org servers we've set up PHP to utilize an opcode cache (APC). After a few tweaks, the cache is helping out by almost halving load and CPU usage.
Drupal 4.6.8 and Drupal 4.7.2 are available for download. These are maintenance releases that fix problems reported using the bug tracking system, as well as two security vulnerabilities.