I've noticed a dramatic reduction in wrist strain at the end of the day, mainly due to the shorter movements for the majority of keystrokes, as well as the proper alternation between hands. Both are hallmarks of the Dvorak layout's primary design requirements.
Regarding impact on programming efforts, My biggest complaint is that the brackets are on the number row instead of just above the home row, but when I'm writing Python code, I use them far less, so it's not much of an issue; when I'm writing PHP, C, or Java code though, it can get a bit annoying, but it's a good trade-off since the +/= and -/_ keys are now closer at hand.
For my editor, I've been using Vim for longer than I've been using Dvorak, but I've never used the hjkl keys for normal movements; I bought keyboards that specifically have the arrow keys right under the Enter key, so moving to use those is very simple, and allows me to use Vim without having to remap any of the normal movement keys.
In all, I highly recommend the switch, especially for anyone who plans to do a lot of typing in their daily routine. The benefits have far outweighed any of the drawbacks. And purchasing a purpose-built Dvorak keyboard will be one of the best investments you can make. I personally love and highly recommend the TypeMatrix keyboards , not only for their great layout, but because it has a physical toggle switch for moving between Qwerty and Dvorak layouts, which is priceless when you want to be able to play games that aren't friendly to non-Qwerty layouts.
I have a similar use as you (programming/English/Portuguese) and I used to use deadkeys for accents. They are handy for Portuguse, but are a pain for programming (need to type things like ` and ' twice). Now I use a key modifier (alt+gr) for accents. It's a little bit more awkward to type accents (need to use 3 keys for an accented letter instead of 2) but usually I just leave the accents out in informal writing (emails) and most writing I do is in English anyway (papers, blog posts, etc), so I don't need to type accents that often.
I have the matrix keyboard that nuclear_eclipse mentioned and it's truly a good keyboard and the folks who make it are very nice. But I don't recommend it for programming because the alt, ctrl and meta keys are in an awkward place (to my taste). So I have one but end up not using it.
I agree that it'd be nice if the braces and brackets weren't in the number row, but it's so nice that all the other punctuation characters are very easy to reach. In fact, I think that dvorak is a great layout for programming.
I first switched the keys (took off the plastic cups and moved them around) of a qwerty keyboard to dvorak and setup a keymap. I later purchased a keyboard by Typematrix which is incredible.
I have been typing in Dvorak for ...8 years. I would never go back to qwerty, and even now when I'm faced with a qwerty keyboard I can sense the tension in my fingers. Needless to say that switching helped my hands heal, I was forced to learn how to type from scratch again (thus learned right this time), and that I can type at least 20% faster without any strain.
Qwerty is like child molestation, only unprosecuted.
Took me about a month to get into it and back up to my QWERTY speed. After two months I was faster and more accurate than with QWERTY.
I didn't bother to switch the keys around, instead I used the fact that the keyboard no longer represented what I typed as an opportunity to learn to touch type with the dvorak layout - I printed the keyboard layout and taped it to the bottom of my screen as my visual clue and then chucked it away after the second month.
Also, I have to admit to a minor amount of schadenfreude whenever someone else tries to type on my 'puter.
My keyboard is qwerty, so i will quickly unlearn to look at it.
I have a feeling that it really is better designed. Home row fells so much more productive.
As i slowly type at 30 WPM in qwerty it deosnt look like a huge drop to start at 10 again.
I would learn qwerty if I were you and only switch if you have pain that other, easier fixes don't help.
About people not being able to use my computer, I actually like that ;-) but if someone really needs to use my laptop, all it takes is to click on the keyboard layout switch in the gnome panel bar. One click.
About Ctrl-C,v,x, for me the key is to have Ctrl where capslock is.