It's time to rewrite our site, which would include the front page. I want to move from tables to css. So far we are in the top 10 SERP's on our major keyword, and I want to stay there. I've followed Brett's rules or tips on how to design a good site, and I intend to follow those rules on the next site. I am planning on keeping some of the text from my home page, but changing the navigation and layout of the page.
Other things I intend to do by using CSS is to bring my content closer to the top of the code, and better manage my heading tags and such. I also want to make my code validate to W3C, which is does not do now.
Have many of you had success with an overhaul of your site and still maintaining your rankings?
I have done EXACTLY what you are describing, down to the letter. We had a one month drop in positions (very minor, a few spots), and now we are stronger than ever. We cut down our page size in half, and it's a much cleaner site now.
If memory serves, we switched right as Google started dancing, so when they did their monthly crawl it was already switched...
I wasn't able to get the css part to work (internal politics), but 90% of my site is now W3C HTML compliant. I had to abandon netscape 4, but if your page is HTML compliant it will work in every common browser in use today (i have a different stylesheet for netscape thats it).