Get Last Logon Time, Last_Logoff time, Mailbox size and Item_Count (Exchange_2007)
This feature was removed from the Exchange 2007 UI.
From the Exchange Management shell:
Get-MailboxStatistics | Select-Object DisplayName, LastLogonTime, LastLogOffTime | Format-Table
The item count and mailbox size can also be obtained:
Get-MailboxStatistics | Select-Object DisplayName, ItemCount, TotalItemSize | Format-Table