Microsoft blogger Ryan Gavin wrote a post about the new features in Windows 8.1's Internet Explorer 11, you can read it over here. Here's a short selection:
More beautiful, touchable favorites: Full support for Favorite sites with folders and custom tile pictures that are more personal and always stays in sync with the desktop and across all your Windows 8.1 PCs.
Your sites first: The most important part of the screen is available for your sites with a single, unified interface with tabs and address bar at the bottom optimized for fast access and touch.
Reading View: IE11 also brings Reading View, which displays text from the Web in a beautiful, full-screen view within the browser. Making sitting back with your Windows 8.1 tablet and reading easy and enjoyable.