Quick note: Internet Explorer 8 Beta 2 breaks facebook Chat, Online Friends and Profile Videos. You'll constantly get JavaScript errors. At this moment there's a simple workaround: Go to Tools > Compatibility View Settings and add facebook.com to the list of sites. Henceforward IE 8 Beta 2 will render facebook in IE 7 compatibility mode.

As a shortcut you can click the newly introduced Compatibility View Button right next to the URL in the Address Bar:

This will immediately reload and rerender the current page in IE 7 mode. The button will only be offered when IE notices that it makes sense.