In preparing for Drupal 7 we need to review our existing upgrade docs (http://drupal.org/upgrade/) to make sure that they work for D6 > D7. Aside from actual testing of the guide (all the way through) it also needs to be reviewed for style guide, grammar, etc. This issue should be used to track the review and note when it is complete.
Ideal deadline is complete before August 14, 2009
This is part of the Drupal 7 documentation effort: http://drupal.org/node/515870