Drupal is growing so fast that I'm not able to catch up. While they've made Drupal 6 so much easier for customization and theming, the functions have also opened up much more.

Then there's Aquia drupal - a commercial version of Drupal with support services. Then Drupal 7 is going to be released. So might as well learn up Drupal 7 theming before upgrading it.

Cheers to Drupal