As a matter of fact, I'm typing in Dvorak right now. I use Dvorak on my computers at home and QWERTY at work.
Overall, I would say it has not been worth it to learn Dvorak. Now, I can type in either one more quickly and accurately than a lot of people can claim. However, I can't type in either one as quickly or accurately as I used to type in QWERTY alone
before. In time, I might eventually reach that level in both, but... will it have been worth it? It's worth it to me to continue with both now that I've made it through the most difficult part, but I don't know that I would have made the same decision if I had known what I know now--not knowing was probably the biggest factor in deciding to do it.
A bit about my experiences:
If you're going to make the switch, make sure you have a good chunk of time set aside where you won't have type anything critically important. At least a week. I found that when I first started training my body to type in Dvorak that it confused my ability to type in QWERTY. Typing at all became even more frustrating than trying to use the mouse with your off hand (which I can also do decently now). By the time I had taught myself to type decently in Dvorak, I couldn't type in QWERTY to save my life.
I found it was really inconvenient to change the keyboard settings on every single computer I used. It's also very impractical to, say, pair-program with a QWERTY user on the same machine. One or the other is always forgetting to press the shortcut to switch formats before they begin typing. Annoying.
It only took a week to learn Dvorak... But I spent the next month or two learning how to comfortably use both!
If you want performance, my suggestion is to pick one or the other and stick with it. You can type quite well in either, really.
Dvorak is a little bit easier on the hands--and kind of fun.
QWERTY is everywhere!
I found this site helpful:
ABCD: A Basic Course in Dvorak
-- Daniel Terhorst