Well, here it is, my first attempt at rebuilding my website in Joomla. Of course I'm not ready yet, but most things should work.
Let me explain the things that won't work and that are not going to be fixed:
- incoming old url's except those for Dilbert comics

Things that will be fixed:
- article contents
- lost translations
- weather page

And I'm still thinking about:
- re-doing the articles
- transferring comments
- cleaning up old downloads

But, for now, it works !

Encountered problems:

1. Joomla SEF is a pain in the ass when you want to add your own rewrite rules.
    In the end I just added a rewrite to a script, and let the script do the redirect.

2. Joomla SEF even prevented Cacti from retreiving the apache status, I had to add a really stupid rewrite rule:

   RewriteRule ^server-status([.]*) server-status$1 [L]

3. Simply disabeling the redirection plugin in Joomla creates interesting errors

   PHP Fatal error:  Call to a member function toArray() on a non-object in .../html/components/com_content/views/article/view.html.php on line 242

4. I've added a Sitemap (Xmap). I hope that the search-engines find it.

5. I've created my own 404-error page, included the sitemap on it.

6. Added a contact-page (FlexiContact), nice pictures !

7. The template (JMint) from themegoat contained some hidden URL's linking to www.deposit-poker.com/party-poker-bonus , www.mdahosting.com/hostgator-coupon , www.themegoat.com and www.wordpressthemesfree.org.  Thanks to this posting (forum.joomla.org) I removed those links.

8. Changed the frontpage slideshow to have 6 pictures (hint), and slowed it down a little.