I don't know about disadvantages for programming, but there are a few main disadvantages if you are using qwerty now (which I'm sure you are).
1. You'd have to learn a new system - I considered it for a while just for fun, but I was reading that it is more rare than you think to be proficient at both.
2. I don't know where you live, but wherever it is if you typed this on a qwerty chances are pretty high that everyplace you could possibly interact with a keyboard would also have qwerty. So you'd have to stay proficient at qwerty, which would certainly be a detriment to your dvorak proficiency.
3. Actual typing studies have shown that dvorak isn't any faster than qwerty.
The only thing that could potentially be good is lower risk of carpal tunnel syndrome, I'm not sure how much data there is to argue that though.
Edit: On a lighter note, perhaps it would ensure that you actually pressed all the keys necessary to complete words when typing.