The database copy layout the tool provides assumes that each server and its associated database copies are isolated from each other server/copies. It is important to take into account failure domain aspects when planning your database copy layout architecture so that you can avoid having multiple copy failures for the same database.
Hopefully you will find these changes worthwhile in your deployment of Exchange 2010. Now, go tryout the new version of the calculator and let us know what you think. Alternatively, you can check out what else has changed by reviewing the Updates Tracking page. The main article has also been updated.