I'm in the Thesis camp as well. Single click layout changes for 1, 2, 3 columns all with adjustable sizes, menu driven font control, etc.
Custom directories for css and layout additions make upgrading a customized blog to a new version of Thesis a breeze. I have upgraded several times without a hitch so its easy to stay current.
I especially like the teaser layout option (one sticky post with configurable number of excerpts on the home page plus different layout options archives etc.) ...check out the teaser layout here:
Huntsville Real Estate
(never mind the colors and graphics ...having someone working on that as we speak)