This Gene Steinberg article previews some of the new features that are coming in Outlook Express, as well as reporting that Mac Office 2001 will leapfrog it's Windows Counterpart.
Nothing real exciting there - but he does get some Microsoft quotes regarding OS X Support for their applications.
Internet Explorer and Outlook Express will be available for OS X "the day it becomes available to customers". Mac Office will take longer, with no specific dates set.