Longhorn design goals
Stephan told conference attendees that Longhorn will:
launch applications 15 percent faster than Windows XP does boot PCs 50 percent faster than they boot currently and will allow PCs to resume from standby in two seconds allow users to patch systems with 50 percent fewer reboots required reduce the number of system images required by 50 percent enable companies to migrate users 75 percent faster than they can with existing versions of Windows.
I like this bit too:
Stephan said Microsoft’s goal is to allow administrators to install Longhorn on new systems in 15 minutes.
Read more here