iPhone + Exchange == IMAP
Updated 2007/07/06: Updated link to iPhone manual.
"Note: Exchange email accounts must be configured for IMAP in order to work with
iPhone." -iPhone Manual, page 44.
Prediction #783: Help desk folks nation wide will get flooded with queries on Monday morning checking if Exchange is configured for IMAP. Meh.
In most of the organizations I know, the answer would be (in the kind words of a British friend): "Not bloody likely."