Drupal 7 is a great improvement over 6, I can't wait for it to be released. However it's progress is eclipsing what could be an even greater improvement to the Drupal ecosystem and that is Views 3
Views is one of the most popular and most useful Drupal modules. Views 2 allows a huge amount of flexibility. Views 3 takes this to an almost unbelievable level.
However the documentation is still catching up. One of the features which has been added is support for SQL group by clauses.
