Japanese keyboard layouts are not less standardized than Western ones. I'm typing this on a Lenovo Thinkpad, and its keyboard does not mirror a desktop keyboard closer than usual. By "usual", I mean that on a laptop keyboard you are guaranteed only the 4 rows above the space bar and the space bar itself. Everything else is at the whim of the designers of the laptop. Wait! Beside the space bar, you are actually guaranteed only the 3 rows above it, because if you don't watch out, you might be robbed of the key on the left of the 1 key, if the designers deem it redundant.
If you want to touch-type modifier keys - I do - then you'll have to be selective when buying a keyboard, be it for a desktop or on a laptop. On my Thinkpad, with the Wide Mod I use, I have got a key right under my right thumb, but I ignore it because if I didn't, then my fingers would start expecting to find a key that will not be available on a desktop keyboard. And when it comes to quality desktop keyboards, the only keyboard models I've found to have a sane layout for keys on both sides of the space bar are the Unicomp keyboards. A sane layout means that the Ctrl and Alt keys are aligned with the keys above them.
As said, there are two versions of Japanese keyboards: one for Japanese typists and another for English typists. This is something I've learned from a reliable source, e.g. a Japanese man passionate about keyboards.
The advantage of a standard Japanese keyboard layout are that:
- you can retrofit a laptop with a Japanese keyboard;
- Japanese keyboard layouts are here to stay.
Neither advantage applies to a DataHand, or any other ergonomic keyboard I know.
That indeed is the reason I stayed away from them.
On the other hand, thumb-shift keyboards are indeed a specialty, therefore you are unlikely to find them in all shapes and sizes.
So, I looked into Japanese keyboards, and the only issue that stopped me from going the Japanese way was that I didn't find enough resemblance between Japanese desktop keyboards and laptop ones. Enough resemblance, I mean, to touch-type blindly on both.
Cheers.
Dvorak typist here. Please take my comments with a grain of salt.