The IE team continues to post news about IE7, including an in-depth look at their approach to tabbed browsing. There's lots of interesting stuff about how tabs will interact with the browser window and third party helper apps / toolbars, but long time watchers of Microsoft's legal battles will certainly enjoy this paragraph...
Another example of what makes this challenging is that IE and Explorer windows share the same code for the frame and chrome (toolbars, menus, etc.), which means there are more code paths and different types of interactions with the hosted view (in this case, a ShellView) that were required to continue working after adding tabbed browsing to IE.
Remember when a post like that would have made its way into evidence? Good times.