Well, you can do this like this:
1. Go to Tools>Analyze>Documenter
2. Select the tables you want from the tables tab, or hit Select All.
3. Click Options in the lower right of the form
4. Deselect Properties and Relationships in Include For Table
5. Select Nothing for Include for Fields, and Nothing in Include for Indexes
6. Click Ok, and Ok.
This will generate a report by Table of who has what permissions based on User and Group.
I am not sure if there is a way to do ths by User, for example.