PHASEIV  KeyRemap4MacBook is a very good (japanese) alternative for Doublecommand users.

KeyRemap4MacBook is able to remap functionality for all modifier keys, remap keys to Emacs-mode

and SandS-mode and provides EISUU and KANA options for japanese keyboards.

There are several other cool settings, and if used with the PCKeyboardHack extension you can use

F3, F4 and F5 for hardware volume control while F8, F9 etc. keep working for Expose and Spaces.

Minor downside is that the remap setting(s) need to be applied through the terminal, but once its set

the program performs very well and stable. (version 2.3.1, MBP 2.4 SR)

Check the developer's site for an overview of the remap options and how to apply them.  
(Version 2.3)