The CSS is empty mainly because I had done this theme as a test to simplify and expose Drupal/PHPTemplate's main features for designers at work who weren't super-experienced at digging through CSS. (As DC quoted on his page)
Placing both sidebar markup sections below the main content is a definite possibility. One other thing that's come to mind as missing is more accessibility features like anchors, access keys, etc.
And I forgot to wrap the post information and terms in conditionals in case they aren't being displayed to avoid printing out empty divs. Actually, on my wishlist for phptemplate is finer-grained control of date/time/author variables for a node (instead of just $submitted).
-Rowan