Summary
Overall, although it does have some problems, AD is an extremely powerful administration tool for managing multiple domains. With a little bit of careful thought and planning, you can manipulate your AD to give you the greatest flexibility, no matter what your situation.
AD and SQL Server combinations can be effectively used (as they were for Henderson) to give you a very powerful security system and data storage area, by implementing common attributes such as the GUID within SQL Server.
So get out there, give it a go, andmost of allenjoy yourself!