This is the script that cost me near 2h of googling on the Internet.
What does it do?
It exports a list of users with custom given attributes, members of groups in an OU you specify.
This script plus some basic Excel processing helped me to find out how many Citrix users we have in all groups we use.
Get-QADGroup -SizeLimit 0 -SearchRoot 'ww.contoso.com/OU/AnotherOU/Groups/Global/Citrix' | Get-QADGroupMember -SizeLimit 0 | select NTAccountName,AccountIsDisabled,Name | Export-Csv C:\TEMP\all_my_groups.csv