In 2011 we migrated a number of clients over to a large Aegir installation. This is on a server 100% optimized for Drupal, fully monitored and running on cloud server at Rackspace. The Aegir hosting system allows us to automate many of the common tasks associated with deploying and managing large websites.
Aegir makes it easy to install, upgrade, deploy, and back up an entire network of Drupal sites. This makes Drupal upgrades much easier and safer as we can move a site between Drupal platforms. For clients looking for an affordable hosting option with business-class power, Aegir has proven to be a great option.