Proper roaming profile management so medium sized networks don't have to faff around licensing 3rd party profile management software.
Also, a group policy setting to enable less of the constant bombarding of users with requesters.
Are you sure? Are you sure you're sure.
This is why users ignore important messages. They are de sensitised to them.
Admittedly, they are less of a problem post vista.
This would have a huge effect.
Speed up boot and logon times to a point that the face recognition has clocked you whilst you are still sitting down and by the time your arse hits the seat, your desktop is ready for you.
Intelligent eyeball tracking. This technology all ready exists. Windows can work out which window you are looking at. It can make an educated guess as to whether that's where you want to be typing. Have that switchable in case it gets very annoying.