Microsoft published a technology overview of Internet Explorer 7 RC1

Internet Explorer 7 RC1 includes advancements in security and browsing experience for end users, functionality and compatibility for developers, and manageability for corporate network administrators. With this build, Microsoft has also made enhancements to the fit and finish of the user interface, completed CSS platform changes, added language support, and included an auto-uninstall feature in Setup, which automatically uninstalls prior betas of Internet Explorer 7, making installing the new build even easier. Read the Technology Overview to learn more.

Technology Overview: Internet Explorer 7 RC1