Scott,
If GAM is working for you, you could use the reports feature in the GA Admin Control Panel. Click the "Reports" tab, then "Additional Reports" tab. The first report is "Accounts Report". It contains a lot of information ( see below ), including the last login date.
Accounts Report fields:
date, account_id, account_name, status, quota_in_mb, usage_in_bytes, primary_account_id, primary_account_name, creation_date, last_login_date, last_web_mail_date, surname, given_name, service_tier, channel, suspension_reason, last_pop_date, creation_time, last_login_time, last_web_mail_time, last_pop_time
Once downloaded you could narrow it down to the info you need. (ie account_name, status, last_login_date, last_web_mail_date, last_login_time, last_webmail_time...)
Steven Bell
Application Specialist
Spring Independent School District