Just a heads up to everyone thinking about installing Office 2007 Beta 2 Technical Refresh (B2TR), the download is a patch and not a full install. This mean you must have Office 2007 Beta 2 installed before patching to B2TR.
Our local guinea pig, Adrian, (just kidding 
) uninstalled Office 2007 before installing B2TR and he encountered this error dialog:
This blog post on the SharePoint team blog announced this particular update process, but it wasn't clear from the post whether this happens for all Office 2007 Beta 2 products or just SharePoint. I just wish the download link for B2TR was clearer about this.