I have been programming for quite a while and I have been told about the "Programmer Dvorak" keyboard layout. It would be interesting to hear people's views on this to help me decide whether I should make the switch.
The main things that interest me are:
I've been using Dvorak since 5.5 years now, the standard Dvorak layout, on a US or UK keyboard. This means I've always typed blindfolded. You get used to typing blindfolded fast, even for the "special programmer keys" like square brackets or the pipe. Most of these keys are the same as on a US keyboard, except the ones around the return and backspace keys.
Since I've lost the speed I had achieved using QWERTY I can't tell whether I'm actually typing faster, I would say marginally, but the biggest benefit is that I type more sedately. If you type very fast with QWERTY, it feels as if your fingers had epileptic seizures. Not with Dvorak as around 70% of the keys you press (English language) are on the middle row; on QWERTY for 70% of the keys you are not on the middle row.
To answer your questions:
If you decide to switch, do it the hard way. I printed out the layout and switched the layout on my Mac. Then I forced myself to do everything with Dvorak plus now and then typing exercises. Switching is terrible the first days, especially if you want to "quickly write an email". Don't switch back then! After two weeks you will achieve a reasonable speed, and from there it's an easy way to top speed. And you won't loose QWERTY; I type on QWERTY less than once a month, but after a few words I can again type blindfolded. I assume getting back to speed can be done within a day.