I actually recently came across Japanese layouts because a user requested support in http://typing.io, a programmer's typing tutor I work on. I like the smaller space bar but dislike the shrunk delete/backspace key [1]. Backspace is already hard to type because of its distance from the home row. The problem is even worse for programmers because the right pinky not only needs to type most of the symbol keys, it also needs to correct typos made when these symbols are mistyped.

[1] https://discussions.apple.com/servlet/JiveServlet/showImage/...