[Dvorak user anecdote:] If I need to touch-type on others’ computers, it’s annoying. I personally touch-type only when I write prose longer than a few sentences. For everyday stuff it doesn’t bother me at all, I just need to look at the keys often enough, otherwise my brain resets to Dvorak; if I see the keys, I can almost touch-type normally on QWERTY.

(If I need to write more than a couple of sentences, I usually switch the layout and remove it before leaving the computer.)