Facilitation by visual note-taking seems a fascinating and challenging profession. Listening is hard, and you're accountable in real time, in front of everybody, for capturing what was said in a helpful way.
I'm sure it helps to be a "visual person", but that alone is not enough. You have to absorb what's being said by people with different ways of thinking and communicating, some more "visualizable" than others. In a well-facilitated meeting, the participants shouldn't feel their thoughts are translated into visual form so much as reflected back to them. At least that's how I imagine it, and while Smith gives lots of encouragement along with her advice, it still seems very hard to me.
On top of that are the challenges any facilitator faces. There may be tensions within the group due to personalities or politics. There may be resentment at having a facilitator at all. Often people's thoughts will not be fully formed — that's probably why they're having the meeting in the first place. And the subject matter may be highly specialized; I assume a good facilitator does enough homework beforehand so they don't have to interrupt every five minutes to ask about basic terms and concepts.