Well, there isn't much more to say for now, apart from trying to focus as much as possible on the content of this web site.
As I write the web site, I continually adapt my XSD and XSLT template to match new XML tags I come up to help me write the contents. As a "catch-all" fallback, I've left the possibility for me to write raw HTML tags in my XML documents, though over time these will be replaced with my custom-made tags (with eerily similar names to their HTML counterparts).
Also, I may have to struggle a bit to make my web pages more "accessible" to disabled users, and potentially also some of those text-to-speech technologies. My understanding is that they would easily break on my XML code, though the static HTML pages I generate as a fallback should work fine. How to test?
Finally, even though I currently think I "nailed" making my web pages gracefully degrade on smaller and less powerful browsing devices, I could still make my pages render specifically for some browsers like Opera Mini or the mobile Safari used on the iPhone.