about the SD card, a micro SD card would stand nice on a DX
I agree with above about touchscreens.
They are very nice, but nothing beats buttons!
The touchscreen is good for annotations or a virtual keyboard.
Basic buttons that are much used like 'menu', 'enter', 'next/prev page', 'power', and perhaps a couple of function and direction keys would do great! (eg: volume buttons for mp3, a button for search/dictionary/bookmarks).
The meaning is to be able to be able to use the device even if the touchscreen wears out and fails; much like it was possible to operate the Windows operating system by just the keyboard, in case the mouse failed (or mousedriver was not loaded)
And I would get rid of the keyboard altogether and use a software matic keyboard with a pen and the touchscreen.