On a traditional Standard (nee Smartphone) device the start-menu items are arranged into a 3×3 grid, you can navigate these quickly using the numeric keypad. On a landscape device the items are arranged in a 4×2 grid so this is impractical. Instead the QWERTY keys are used, or to be exact:-
Another helpful feature which was introduced in one of the AKU updates to Windows Mobile 5.0 was a scrollbar so that scrolling off of the current page of menu items would advance to the next or previous screen of items (Equivalent to pressing soft-key “More” or Back button). The scrollbar give you a visual indication of where you are within the menu items which typically span 5 screens in landscape orientation.
One part of the shell which has not received the same attention is the Settings screens. Unlike the Start Menu there is no scrollbar, you must advance to the next screen using the last list item (this is not offered as a soft-key item). This means that in landscape orientation only 6 settings items fit on a page. A few changes here would allow more items per screen and consistency with the start menu behaviour. On devices with a built in scroller such as the HTC S620, T-Mobile Dash etc you could quickly scroll through all the configuration items.
Another place where this behaviour is not followed is the Pictures & Video application. Here the items are again arranged in a 4×2 grid on a landscape device however the key assignments are really wacky:-
You can see that the application is hard-coded to use the numerical keys and so there isn’t a shortcut to select the righthand column.
These help to illustrate another area where developing for multiple screen sizes and layouts can introduce complications. You should try to follow best practices to offer appropriate shortcut keys in your application, just be aware that even Microsoft have missed some of these issues in the platform itself.