Creating users and permissions have some limitations when you're working with a main parent account and trying to give one person access to numerous sub-accounts.
1) Certain filters in reporting are not accessible for parent account users when looking at sub-account reports.
2) You cannot use the same email address within numerous sub-accounts without using tricky upper/lowercase spellings.
I wish this would be streamlined a little better for users with multiple accounts. However we have found that the user abilities are a lot more advanced over other platforms that do not even allow parent/sub-accounts. Review collected by and hosted on G2.com.