I have been using Dvorak all my life - I never learned to touch-type with QWERTY - and for the most part I'd agree with this author's conclusions. While my typing speed is higher than average, it's not so much higher that I can confidently credit the use of Dvorak, and in any case I have never found that typing speed has any significant effect on programming productivity.
Contrary to this author's experience, however, I very rarely need to do any serious typing on anyone else's computer, so the fact that I become an absurdly clumsy two-finger typist in front of any machine but my own is nothing more than an occasional source of amusement for my coworkers; nor do I especially mind their reluctance to jump in on my machine and type for me. I can imagine how this would be more of an issue if you worked in a pair-programming shop, but I never have. In any case, this problem has been trivially solved for decades now, on every OS - you just enable a little built-in menu bar widget which selects the keyboard layout, and you can flip back and forth in less than a second.
I type faster than most people, getting 120wpm for sustained periods of time. I did so before switching to Dvorak and I still do (although not with qwerty). For me it was as simple as training to avoid tensing my fingers and feeling strokes of keys rather than individual key presses.
This makes me think that neither Dvorak nor Colemak are the best layouts for me, but rather something that optimises for di- or trigraphs. This will be pretty language dependant, even moreso than Dvorak/colemak, and as someone who regularly write in three languages it is probably just easier to stick to something with a more general design.
The capewell-evolved layout does so for English, and it can really be worth checking out.
Contrary to this author's experience, however, I very rarely need to do any serious typing on anyone else's computer, so the fact that I become an absurdly clumsy two-finger typist in front of any machine but my own is nothing more than an occasional source of amusement for my coworkers; nor do I especially mind their reluctance to jump in on my machine and type for me. I can imagine how this would be more of an issue if you worked in a pair-programming shop, but I never have. In any case, this problem has been trivially solved for decades now, on every OS - you just enable a little built-in menu bar widget which selects the keyboard layout, and you can flip back and forth in less than a second.