Thought Wordpress users might want to see the results of a test we're running that compares the SEO of Wordpress to Drupal and Joomla. The systems are obviously different (as pointed out in the article) but the results are pretty clear so far:
http://www.alledia.com/blog/seo_competition/january_search_engine_optimization_test_update/
You note in a comment that "someone could probably drive a truck through the methodology here." I've nothing to add here... Except!
Your 'test' would benefit if you could provide some details on how the software you're using calculates these scores. I don't know about anyone else, but search engine click-through numbers would rate (at least) Drupal a hell of a lot higher in my book.