Can't speak for Eliezer, but for me, I was able to use my computer for normal tasks (but slowly, and with lots of errors) after probably 5-7 hours of intensive practice, but the frustration did not subside until after the 2nd or 3rd week. This was in high school, though, so I'm not sure how long it would take an adult.

That said, I haven't "unlearned" qwerty. I use Dvorak on my ergonomic work keyboard, and qwerty on every other keyboard. The different feel of the keyboards successfully triggers my brain to use the right layout, and I don't have any trouble switching between them (I don't even notice anymore that they're different layouts).