Having used hanwriting for android a little more extensively, I've decided that its physical keyboard support is terrible after all. I was already dubious about it, but what really kills it for me is the way it provides suggestions.
For English, hanwriting's suggestions are OK, and although a bit fiddly, you can kind of get around stupid suggestions by simply dismissing them.
For Japanese however, you need the suggestions to convert your hiragana into kanji, and the only way to do this is to either accept the default suggestion, or physically press the kanji that you want to use. In other words, there is no way to select the kanji using a physical keyboard.
In essence this means that writing Japanese text will sound like "hack hack hack - tap - hack hack hack - tap - " etc. Not that the noise annoys me, its the constant flipping between typing and poking that I can't get used to. After all, once you've taken your fingers off the keyboard to poke the screen, you've got to get your hands back into the typing position by finding the F and J buttons, which somehow feels like a huge impediment to the fluidity to writing something.
For the sake of being able to actually write an email to my wife without going insane, hanwriting is no longer my default IME.
That said, if you spend much time looking up complicated Japanese characters, hanwriting still has its handy kanjipad.
EDIT： Got an email back from the developer, apparently the next version will be clear of these bugs! On the other hand, that means I might be obliged to write a rereevaluation post... I've really done it to death already.
Looking forward to that update though!