I remember seeing a Japanese keyboard sometime ago where each button mapped directly to a Japanese letter, for example there was keys for か and き.
Oftentimes I feel that my typing in Japanese is very slow and sometimes I wonder if it would be helpful for me to use a keyboard like that, or at least change my computer's configuration so I could type that way (though it would require painting over my keys, or memorizing each letter). It seems clear that this would be much more efficient in terms of the reduced number of strokes for most of the letters.
My question is whether this type of keyboard/input system is used commonly in Japan, or if Japanese people have just gotten used to typing "k a" for か.
EDIT: I am looking mostly for information about how many people actually use a keyboard like this on the desktop, and am not much interested in mobile.
KANAthat will enforce this behavior. Like you say, though, you'll have to re-learn the keyboard.