I wanted to let others answer before me because I'm still very new in this (for the reference, I know all the letters and maybe a little less than half of punctuation and special keys, I still need the cheat sheet for the other half; and in this post I erased as typos almost as many characters as are left; that's after a few tens of hours of practice over a month).
My feeling is that the device is a functional tool, as any standard keyboard or mouse (and requiring as much of tuning as a many-buttoned mouse in a gaming context), but that the human holding it is not (yet).
I would say that it's like a keyboard you have to touch-type (and you cannot reuse your reuse your existing touch-typing skills), so it requires a lot of training before being usable. Unless you are very bent on optimizing perfectly the layout, the time spent tuning will be negligible compared to the raw training time.
I did buy mine for a very similar use as yours, except that it's while walking instead of while meeting. It's what I call "blind typing" (not sure whether it's a real term or not), in that once you can touch-type decently, you have to learn to type without any visual cue on what has been entered previously. That means not only missing typos, but also having to hold all the state in your head instead of having it under your eyes, and you might be underestimating how large it is (I know I did).
Also note that on top of that, you will have to split your attention between holding the state and the meeting (with people around you losing the non-verbal cues that you are typing). Some people have more trouble than others with splitting their attention. You will likely need for some time a three-way split, between a high-level state (what ideas have already been written, what the current paragraph/bullet-point is about), a low-level state (what the current word is and which letters have already been entered), and the world around you.
Lastly, be aware of the low typing speed, at least in the beginning. I wonder what kind of speed get those with years of experience, but I would expect years of full-time practice and layout tweaking before being able to perform real-time transcription. You will reach sooner the point of being able to take the kind of notes where they are just memory helpers to be expanded shortly after the meeting.