I’ve seen some pretty long file names before, but “Changes in Functionality from Windows Server 2003 with SP1 to Windows Server Code Name Longhorn.doc” would appear to hold the new Microsoft record for the longest name for a guide. This is a very good overview of the changes you can review in Beta 3.
The guide can be downloaded from http://technet2.microsoft.com/windowsserver/longhorn/en/library/0e0d96cd-935b-48d0-b5ba-c70a979fadbc1033.mspx?mfr=true but I will warn you that the Microsoft download servers are a bit busy right now so you may want to hold off until later this weekend.
The online web version is at http://go.microsoft.com/fwlink/?LinkId=87080.
The Word downloadable version is at http://go.microsoft.com/fwlink/?LinkId=87488.
While you are at it, you might as well download the “Reviewers Guide“. Again, very good reading.