Keep it simple
As it turns out, the conversion from the old design to the new has gone surprisingly well. I hope that came from keeping the new design simple. There's only three images in use... there's the repeating background, the logo, and the horizontal rule. That's it. CSS wise, there's only one font: Arial. My new motto: keep it simple.
My HTML structure has changed enough from the past that there really wasn't much that was re-used. Hopefully, the new structure will be more accepting of a redesign.
One of things I did with the structure was include the breadcrumb navigation at the top and left everything else at the bottom. Moving the navigation to the bottom moves the content higher to the top and should improve Google relevance. Hopefully it'll be easier to use from an accessibility point of view as well.
Movable Type rebuilt all the files with ease. I'm still using version 2.6 and not 3. V2.6 still works fine for me so I have no plans to change. One thing I did do was test out the new design first. To do this, I created a new individual entry template so that both the new and old design would get generated on a site rebuild. Once I was happy, I just changed the templates around and voila, it was done (well, except to change the template on all the other archive types).
I changed around the directory structure slightly to make it a little more expandable. Now that I have a new member in the family, I wanted to set up the home page to be a jumping point to any family member. That meant moving my stuff to a sub-folder aptly named /jonathan/. I left the entries in the /archive/ folder, though, to avoid setting up redirects for the old pages. There's a few links to my site out there and I'd rather not confuse users by killing those files.
Dave Shea talks of huge CSS files but I was able to keep mine under 4k. And I could probably pare that done a little if I wanted. Again, just trying to keep it simple. It even looks half-respectable in Netscape 4 (only half, it'd take some tweaking to get the other half!).
In the end, I think the new design is a huge step forward. I think it's hear to stay for awhile.