In Fall, 2002, I switched to the Dvorak keyboard layout. I had tried to switch before, but learning to type again takes time and as a programmer and avid computer enthusiast, I failed in several less-than-serious attempts to learn the new layout. After switching "cold-turkey," it took me two weeks to be able to type at the same speed I used to type QWERTY, but my hands and wrists have felt much better since. It also took me a while to "re-learn" QWERTY, though. Six months after retraining to Dvorak I still hunt and peck a little when using QWERTY (not often). For me, the cost has already been outweighed by the benefits, and I (hopefully) have many more years of typing ahead to enjoy the benefits of Dvorak typing.
I would recommend Dvorak to anyone who types an awful lot. I imagine you might also view it as a competetive advantage: Dvorak users, on average, will be able to type faster than Qwerty competetors. Not only that, but less injury/pain means more concentration on work.
Dvorak alone is not an ergonomic solution for people who use the computer a lot (like me). You will need to pay attention to posture, the height of your chair, keyboard, monitor, and many other factors to avoid injury. But Dvorak can certainly play an important role in overall healthy working.
It seems like the creator, August Dvorak, was not shy about promoting his keyboard layout. Some people question the integrety of his efficiency studies and cite the lack of other studies to back up the claims that this is a better way to type. My own experience is that I prefer this keyboard layout, but you should probably do your own homework.
For emacs, the switch can be a pain because you're used to typing "C-x" as the first part of almost every command. I found it useful to use the following in my .emacs so that "C-q" behaves the same as "C-x", which keeps the physical keys in the same place. This works with X Emacs and GNU Emacs.
(define-key global-map (kbd "C-q") ctl-x-map)
In addition, it is nice to keep "M-x" in the same place as well:
(define-key global-map (kbd "M-q") 'execute-extended-command)