Exchange 2007? Yes! With all this Exchange 2010 coverage one might forget about Exchange 2007, but not the Exchange team who updated the Exchange 2007 Mailbox Server Role Storage Requirements Calculator to version 17.3.
The major change in this version compared to version 16.9 (released April, 2009!) is a change in the IOPS calculation. This change is to based on the BlackBerry Enterprise Server for Microsoft Exchange 2007 Performance Benchmarking Guide which simplifies the IOPS calculation in combination with 3rd party software.