Hey bros. First of all, Happy Thanksgiving. I am typing between gulps of beer and food preparations.
To verify my qualifications, I use an Ergodox at work and a standard ANSI staggered keyboard at home. Perhaps I am super human or something, but the transition between the two for me is not a problem. After a couple minutes of getting going on each, I do not have much trouble. You are right to assume that the differences between the two are so stark that the transition between them is not that difficult.
Adjusting to use the thumb keys was the most difficult part for me, but once I had that down, things have been smooth sailing.
Switching between QWERTY and my custom layout is a challenge. I am AWFUL at QWERTY these days.
When I had a variety of matrix layout keyboards-Kinesis Advantage, Ergodox, Maltron-that I was switching between regularly, I had some troubles. Each had a different keys in some locations, so that created some issues. Now I worship at the church of Ergodox, so things are going smoothly now.