We have been moving to a single solution for network servers. We are moving towards Active Directory from a Windows NT/Novell environment. Needless to say one wants to plan this out well. From the user vantage point there doesn't appear to be a big payoff. They could store, share, and print files before. It might make it more manageable, but getting there has had its share of frustrating moments. Of course, the network group has been locking down permissions at the same time, so occassionally something stops running, printing, etc..
I believe one of their next projects is moving from Exchange 5.5 to Exchange 2003.