I really love the "selectable rendering engine" in the menus. It is a bit quirky when trying to switch back and forth, but seems to switch okay from the one used to render the page into the one of your choosing.

Also, it was via this release that I learned about the .exe.local directory. There is a "iepreview.exe.local" directory which evidently supersedes the DLL search path (and that is probably how they are able to package all the render engines in a "live" copy of Windows).