So, the bad news is I can’t use a custom 404 page, because my ISP runs PHP as a cgi. (If you don’t know what that means… well, trust me, it’s for my own good.) The good news is that plain ol’ redirects work just fine, meaning I can do the RSS feed redirects I had been worried about. So I’ll migrate sometime very shortly, when I’ve collected my senses and can ask a couple of colleagues to provide emergency messages in the event Something Bad Happens.
Meanwhile, it’s Clean My Office Night, and I can’t tell you how much fun that is! So much that I’ve procrastinated for two hours. I’ll play some podcasts and get to work!
I’m not sure what restrictions your hosting provider puts on you (and I’m afraid I don’t use PHP on a regular basis), so I’m not sure if this would work for you, but it may for some of your readers. I just migrated my blog, and I am handling the dead-link-problem using Apache’s mod_rewrite. Judging from the URL of this page, it looks like maybe you are using mod_rewrite as well (since I don’t see any ‘cgi-bin’ or .php scripts there).
In any case, if you are interested, I posted my notes at http://blog.kaeding.name/articles/2008/07/22/migrating-urls-with-apache