There's a new version of Google Talk: 18.104.22.168. While there's no obvious new feature except for Vista support, it's interesting to look at some additions from the previous versions.
When you invite someone with a non-Gmail address, a new dialog informs you that Google Talk tries to see if that person uses another compatible service, like Gizmo or Earthlink.
Links to Gmail from Google Talk send you to the secured version of Gmail (you'll notice that the URL starts with https).
There are also some new status messages, but they aren't visible yet: "Show who I am chatting with", "Chatty", "talking w/".