thanks for the links to my articles.
I have to agree with you - WP is great for Google SERP (Search Engine Rank Position). My site comes very high in Google for many search terms as well.
Google did a re-index a couple of days ago and this affected a lot of sites - I think the WordPress install was co-incidental.
To ensure you get a good Google SERP for your site I would advise:
1. Ensure your theme validates (using the w3c validator)
2. Choose your WP category names to match your target keywords/keyphrases
3. Ensure your Permalink structure contains the %Postname% (and as little else as possible)
4. Use your Keywords/keyphrases in your post titles
5. Develop a linkage strategy to increase relevant inward and outward links
6. And, get your blog listed in directories like dmoz and/or LookSmart
For more see some of the articles I have at http://www.tomrafteryit.net/category/search-engine-optimisation/
and feel free to contact me (via the contact form on my site)