From the Administration User Browser screen, have an "Export List" button/link that exports all the users that match the current filter into a .CSV or Excel file. The columns exported would match the columns currently displayed: Username, Email, Full Name, Login Details, Groups. No formatting needed, just dump the text as displayed in each table cell into a single field (including carriage returns for multi line entries like Login Details).
This would be much simpler than having to run queries to do this as described at http://confluence.atlassian.com/x/FYJyCw
The end goal is a simple way to monitor who is logging in most often (need to contact the top 50 users), who has had many recent login failures, who belongs to one group but not another, etc.