Explore the glory of Drupal 7's improved render and theming systems
One focus of Drupal 7 has been to empower module developers and theme developers to more easily achieve the look the want for their final output. We added hook_page_alter() where a themer or module developer can alter any part of the page just before it is rendered. At this point, the page is still a raw array that can be easily manipulated.
Similarly, granular theming and a new give themers better tools during the preprocess and template layers for outputting exactly what they want and not sacraficing forward compatibility as new modules/features are added.
This is going to make our lives much easier.