I've been using the Twiddler now about 2 months and have achieved a pretty regular 35-40 WPM. I can write content while standing on the subway, walking the dog, or standing in a bus. It's pretty great.
That said, there are some custom digraphs ("th") and words ("this" and "that") come to mind. How do I find a free key? At the moment, my plan is to take the binding CSV, extract all the chords and then brute force generate all possible chords. If a chord shows up twice, then it's bound; if not, free. Surely there's a more natural way for finding these details (awk skills ought not be a requirement for Twiddler extension ).