I think you're referring to the ArcSDE Privileges Report. It added a tab to ArcCatalog that allowed you to see who had Viewer/Editor privileges over the entire geodatabase or on individual data objects. Unfortunately, it hasn't been updated for ArcGIS 10 as of this date.
At ArcSDE 10 you can use the sdetable -o list_grantees command to list permissions for each user granted access to the table. For example
sdetable -o list_grantees -t dbo.parcels
User Name: GISEditors
Privileges: SELECT, INSERT, UPDATE, DELETE
User Name: GISViewers
Privileges: SELECT
Work by John Karagiannis is what you are looking for, although I don't think he has updated any of the ArcSDE tabs since 9.3.
Here is the latest link I could find - ArcSDE User Privileges Report (9.3 SP1) , but much of this functionality has been added to the privileges routine in catalog at 10