Dan made some comments (via private email) on my previous rant about GoogleTalk. He pointed out that there aren’t any references to this on the web—nobody complaining about being unable to connect, and so on. A little digging lead me to this page on Google’s support site, which details the DNS changes that need to be made to point a Jabber client to a different server.
So, in short, it’s not exactly Google’s fault, except as far as their system is crazy. However, people using Google Apps on their own domain, and using Google Talk specifically, for the love of $DEITY please set your DNS up correctly.