UPDATE: The old question applies only to IE11 preview; browser mode had returned in final release of IE11. But there is a catch: it is next to useless, because it does not emulate conditional comments. For example, if you use them to enable HTML5 support in legacy IEs, you will no longer be able to debug your site in IE11.
<!--[if lte IE 8]>
<script src="html5shiv.js"></script>
<![endif]-->
Read another StackOverflow question and IE bug tracker issue. Microsoft never responded to this, so it looks like they introduced this bug on purpose to steer people into buying BrowserStack subscriptions. Conditional comment emulation worked just fine in preview release.
ORIGINAL QUESTION: When IE11 preview is installed on Windows 7, it comes with old-fashioned F12 tool which allows to change browser modes.
However, if you go to "Tools" menu and select "F12" developers tool, it gets replaced with new developer tools, and "Browser mode" is no longer available.
The only way to bring it back is to uninstall IE11 and reinstall it.
Is there easier way to switch between browser modes in IE11?