Used US and JP qwerty, both are fine after a while, but switching can be annoying (mostly I mix up whether " or @ is Shift-2).

The one thing I hate is the fragmentation of the bottom left cluster. I started out on keyboards with Ctrl Fn Super Alt, but now I much prefer Fn Ctrl Alt Super.

The addon version works on Android.. There’s an issue/“idea” for Chinese support as well. If I recall correctly, though, one of the problems is tokenization (the languages currently supported for example have spaces to separate words).