The Google Talk gadget seems to be adding new features at a faster rate than the actual windows client these days -- today they launched a new multiple user chat interface. The feature is a bit awkward due to the gadget-only functionality, but once you are using it, everything seems natural.
Multi-user chat was hinted at in April through the "Google in your language" initiative -- but it was unclear at that time how the feature would actually manifest itself.
My only gripe is the fact that it's not available in the real Google Talk client or in Gmail. When you start a multiple user chat from the gadget, the friends you invite are sent a link to click on which takes them directly to the web-based version of the client -- let's just hope this is a temporary solution!