Basically, all this does is run the Get-MailBoxStatistics cmdlet and export the results to a CSV file.
Syntax: path\statistics.ps1 <<your-exch-server>>
Eg: C:\Statistics.ps1 SERVER01
this will create the following CSV File:
DisplayName, ItemCount, TotalItemSize (formated in MB's), StorageLimitStatus, Database
This works on Exchange 2010, but I would imagine it'll also work on Exchnage 2007...