Now that I think about it, it would be nice to have a physical *and* a virtual keyboard.
My Palm Pre has a physical keyboard. I also have a virtual keyboard hack for those times I want to use the phone in landscape mode. Since Kindles can be rotated 360 degrees, it would be nice to have a virtual keyboard when not in the standard portrait mode. Of course this would require a touchscreen which I wouldn't mind since my cell has a touch screen and a physical keyboard and they get along well.