However, PowerShell is only available remotely with Exchange 2010, since PowerShell 1.0 did not support remoting. That means the application would have to be run ON the Exchange Server, which is almost never an option. Also almost never an option is upgrading the server to PowerShell 2.0 (I've done it, but no Exchange Server admin will go for it)
So, the fact remains that there is no easy way to get mailbox sizes and counts from Exchange 2007.
Exchange 2003 exposes it easily via WMI
Exchange 2010 exposes it easily via PowerShell
but 2007... all the solutions I've seen involve a lower-level solution using MAPI or EWS and recursion/iteration over all folders in each mailbox. It seems incredibly unfortunate that 2007 should be left out, (big oops there). Any alternatives out there?