I'm really digging the Sandbox theme for WordPress so far. I've not really done much yet - but between Sandbox and the new WordPress Widgets, all my customizations for this blog have been done in CSS and drag-n-drop in the widget management screen. Sandbox has an enormously rich set of classes dropped into every major element of the page, even down to date/time information on posts and category-based classes. I could even drop in some seasonal themes to styles posts for holidays and whatnot. Pumpkins for October, and presents for December!
I did need to add one line of PHP to a Sandbox template, and that was a CSS include to my own tack-on CSS full of tweaks to the Spartan skin. If anything, that's my only feature request so far: Allow skin selection, and then allow the user to specify an additional stylesheet to further tailor that skin. The less I need to edit in files installed from third parties, the less I need to maintain when versions get updated.
I'm also running into a few minor CSS oddities when I view my tweaks in MSIE on Windows. This annoys me, but I only half care to fix them.