I've been evaluating Artisteer, a wysiwyg theme building program that runs on Windows, and I am impressed. With no theme or even HTML/CSS knowledge, you can build a usable design for Drupal, as well as WordPress, Joomla, or just a straight HTML/CSS site very quickly.
One feature I found particularly useful is the 'Ideas' menu, which will suggest random designs for you at the push of a button - either the entire theme, or just portions of it like blocks or header. Very useful to get started with, and then you can start tweaking the details.
The themes are a bit static - you get the standard 1 2 or 3 columns layouts, and you cannot define new regions (yet?). It also appears to have problems with some Drupal features like panels. But it could save a LOT of time on design iterations. And for many sites, it may be all you need.
I'd really like to know what real themers think of the code it generates. It looks reasonably good to me - no tables, all div based at least. Would it be a good starting place for theme work? Can it be extended easily by hand, or does it look like something FrontPage would have produced?
I'm building a new site for my sister's studio in Drupal, and I sat her down with Artisteer to play with designs for it. Here's the current one she built herself. Three hours later she comes up for air, "That thing is like crack! Why did you do this to me?"