After installing Windows 8 Pro, I have 2 different versions of Internet Explorer 10: The "Windows UI" version, which works as Windows 8 UI app, and the regular Internet Explorer 10, which runs in desktop mode.
One thing which bugs me here, is that these two programs don't share settings such as cookies. So when clicking a link within a third party Windows UI program, the Windows UI version of IE pops up and requires me to login, even when I used the desktop IE already for logging in.
In my opinion the thing gets even worse, as the "desktop version" of IE can't be set as default browser, so clicking the "Internet" tile will always open the Windows 8 UI version.