What are Japanese keyboards like?
Well for one thing apart from using the IME with Romaji input they also have a Kana input mode. This link shows the kana layout for use with standard English Qwerty keyboards while this link shows an example of a standard 109-key Japanese Keyboard. Most Japanese stick with the romaji input though.
Why would someone bother to learn kana mode?
The Japanese keyboard layout is more efficient for touch typing in Japanese which can make it preferable to people suffering from RSI. If this is the case, then just as switching to the Dvorak keyboard may alleviate much of the strain from typing in English, typing in kana mode can alleviate much of the strain from typing in Japanese.
It can also be preferable for people used to a different keyboard layout. Standard IME reads the keyboard as a QWERTY keyboard. Someone used to typing Dvorak will have difficulty typing with standard IME. Switching to kana mode instead circumvents this problem. It is easy to keep kana and roumaji layout separate in the mind. Switching between Dvorak and QWERTY is easily confusing.
There is a registry work around to make standard IME work with Dvorak keyboard layout, but for people that have to share computers, or work on other people's computers, editing the registry is not an acceptable option.
How do I use kana mode?
Kana mode in IME works slightly differently than in standard mode.
- * The dakuten (゛)and handakuten (゜) are specific keys in kana mode mapped to the  keys on the QWERTY keyboard or /= keys on the Dvorak keyboard. To add either to a kana, type the kana and then the correct dakuten\handakuten key.
- * Small kana, (ぅぇぉゃゅょっ) are typed by using the shift key.
- * alt-caps lock switches to katakana mode
- * ctrl-caps lock switches to hiragana mode.
Otherwise kana mode works the same as standard mode. Hit space to find the kanji, if the parser does not break the words correctly, use shift+(right arrow) or shift+(left arrow} to increase or reduce the parsed word. This trick is especially useful for non-standard readings.
The best way to get started is to either buy some overlay stickers or print out a copy of the keyboard layout. Always make 3 attempts to find the key by trial and error before resorting to checking the key. Once you have the keyboard layout down, improve your typing speed by concentrating on key groups. Consciously notice common two letter groups and practice them. The faster you want the type, the larger the key groups you should practice. However, most people type at a reasonable speed once many 2 key groups are keyed to muscle memory.
 Same as in standard mode.
 If you are using a Japanese keyboard, this can also be done by using the key to the left of the right ALT key marked カタカナ/ひらがな/ローマ字. Pressing this key will give you hiragana, shifted will give you katakana, and Ctrl shifted will give you roumaji input.