Mike,
I've been a long time user of ACDSee and my biggest complaint with PM is that when you are previewing an image at 100% you have to use the mouse to move the image in it's frame in order to view different pieces of the image.
I really like the fact that in ACDSee the arrow keys move you around the image while it is full size since you can't view an entire 8 MP image on a 1280x1024 screen.
Any time you can take an action that requires the use of the mouse and make it usable via a keyboard shortcut you will make a friend outta me.
Everything from customizable shortcuts to Underscored menu items are greatly appreciated.
If you hold down the Shift key, the arrow keys will move the image around. If you hold down the Control key and the Shift key then the arrow keys will move the image around
faster.
Control clicking on the image will zoom in and out from the point of the click. Also, the scroll wheel will allow you to move through the photos. Shift scroll wheel will change the zoom factor.
(This description is for the Windows version only. The Mac will use Command instead of Control, and Option instead of Shift.)
HTH,
-Kirk