The H9's MIDI can be improved on a number of fronts. For me the issue is MIDI clock. While the H9 will accept incoming tempo, it doesn't really lock onto the clock signal, so with effects like tremolo and the Harpeggiator there will be noticeable drift after a minute or two. I had been emailing support about it and even sent the MIDI clock information from my Boss RC-505 to help. I haven't heard back for a while, so I'm not sure if they're still working on it or have given up. There are a couple inconvenient workarounds, but I just don't understand how units like the Roger Linn Adrenalinn, Boss SL-20 and EHX 8 Step Program can keep such a rock solid tempo yet it cannot be done in the H9.
The Harpeggiator in particular could be SUCH an amazing effect, but without being able to lock on solidly to MIDI clock, it's just a novelty effect.