I just worked thru the ASP.NET Whidbey Personalization HOL. The docs on Whidbey’s new theme feature aren’t done, so this is the first instance I’ve seen on how to use this feature. Pretty cool stuff. The Whidbey Alpha only includes 2 themes: SmokeAndGlass and BasicBlue, but the HOL shows how to build your own (albeit an incredibly ugly one).
Only issue is that it seems (in the alpha at least) that the theme support is something the developer adds. But tools like .Text let you specify custom settings so the blog author can have a custom theme of their own design specified @ runtime. I wonder if later versions of Whidbey will have similar support.