What else is different?
Administrator account is disabled (fix?)
Power Users are mostly gone
Boot.ini replaced by BCD – boot configuration data stored in \Boot directory edited using bcdedit.exe or EasyBCD.
\Documents and Settings replaced by \Users
User Account Control (UAC) prompts for admin password (just like in Linux) even if logged as admin
Run not in Start Menu – add or user the search area
Command prompt to run admin applications now require to be started as Run as administrator
IPv6 is installed together with IP v4. No problems in small networks but conflicts with Active Directory. Longhorn should fix
System Restore now restores (undelete) files not only programs like XP does.
Neat stuff: Flip (Alt-tab) and Flip 3 D (Windows-tab)