In this video, Jon Rettinger (who reviewed the BlackBerry Storm for pocketnow.com), does a task-by-task comparison of Windows Mobile 6.1 Standard (using a Pantech Matrix PRO) with the iPhone. He walks through several items, such as adding a new contact, adding a new calendar appointment, changing a ringtone, and others.

On the Matrix PRO, the sliding panel interface helped a lot to let Jon access certain functions that would normally be buried within the Start or Settings menu. Overall, the iPhone requires fewer button/screen presses to do the prescribed tasks, but of course if you were to use a Windows Mobile device with programmable hardware keys, this would be a different story.