Yesterday Acquia released their commercial supported version called Acquia Drupal and their online set of management tools and support bundled as the Acquia Network. After playing around with them a little, here's my first impressions.

Acquia Drupal is offered as a free download, being licensed as GPL. The installation process is fairly straightforward and doesn't differ from the standard Drupal one that much. You'll see you're able to enter some extra information (the Acquia subscription identifier and key) but the rest is identical. You can skip the Acquia information as you don't need a subscription to use it. After everything is set up you're left with a website very similar to what you would get with Drupal 6 (on which Acquia Drupal is based, by the way).