The use of themes is a hot issue at Drupal-- much more so that at any other CMS.
As one of the aformentioned designers, it seems to me that this is a crucial issue that will be determine the degree to which non-programmers use Drupal.
So this thread is attempts to get designers to sound off about what they are looking for, what frustration they have encountered, etc. Other threads seem to devolve into discussion that are difficult to follow since they discuss issues that those not privy to development don't really understand.
Adrian's discussion is very interesting, but it seems to me that the notion of a templating system that he touts errs on the side of being too 'automatic' (Aidrian-- excuse me if I misunderstand your post). I think what's needed is a way of simplifying the implementation of the strings that Drupal renders. As a non-coder, I would like to have a complete set of Drupal strings (ie. {submitted}, {node}, etc, that can simply be plugged into a css layout. So if you want a search box at the bottom of the page, you just create a 'div' that situates it there. The problem with existing templates is that they are too tied to a conception of how the site should be (search in the 'header', etc.) Someone wrote in another thread that xtemplate uses the !comments to parse the template. When I read this, my jaw dropped. It's using comments to parse the layout?. This is extremely confusing and counterintuitive.