I just received my C3000 from Dynamism, and I think I may be able to address some of your concerns. Firstly, the unit is smaller than the SL6000 and just as comfortable--I tried it at CDW before purchasing the C3000.
Holding it like a regular PDA is very well designed, albiet lacking a directional pad is hindering. In clamshell mode, it feels very well balanced, with a very comfortable weight on th base of the unit. In PDA mode, the location of the CF slot (and thus the protruding wi-fi card) is ergonomically on top, but while in clamshell mode, the card sticks out from the right, causing one's right hand to climb over the keyboard a little longer.
Overall, typing in the unit (as I am doing now) is very comfortable, but dfficult to do standing and back-aching to do sitting! But I'm sure that's true with any PDA. I personally cannot get the handwriting recognition strip (onscreen, not actual hardware) to work effectively.
The whole unit is very attractively designed with a plastic white exterior and silver trim as clean and as oil-sensitive as a fourth generation iPod. The trim, though covered with the thin film from my otherwise clean fingers, gives an especially high-end touch. To characterize it simply, the unit is a bit ricoculous in appearance.
As far as the Japanese goes, the easy-to-remove stickers only prelude the Japanese alphabet-switching keys. However, the amount of Japanese in the software depends on the provider, and I can't give a confident opinion on Dynamism's job because I haven't examined the nooks and crannies where the Japanese is most likely hiding.
