I like the new 2010 theme that comes with WP 3. I think the SEO is OK out of the box. My example is at Kanazawa Restaurants I didn't do much customization yet, just changed the background color, footer code (to display a copyright and year), and I selected one of the header images made available with this theme.
They also configured the script to use wp-super-cache out of the box too.
The source code of the rendered page looks fairly tidy too.