A Real, Installation of Groupwise?
When was the lst time you admin'd a Multi-PO/Multi-Company well maintained GroupWise system?
What is the upper limit of users per PO with Exchange? GroupWise is in the 10's of thousands
What amount of flexibility to move users does Exchange have? GroupWise can and does do it while the user is using their GW account.
There is no limit to the number of resources you can have in a GroupWise system... Even Identically Named Object if need be.
How many Objects can have the same name in Exchange... err or even ADS? eDir and GroupWise... as many as you want... IN THE SAME TREE as long as they are in different context branches.
I could go on.