I've read somewhere, I can't seem to find it now, that in an experiment involving people learning to type, that the Dvorak keyboard didn't have a tangible typing speed benefit in comparison to the QWERTY keyboard. Do you know of any studies about this?
Somewhat. Typists can, in fact, learn to type faster on a Dvorak keyboard, it's just not a big improvement.
Even in The Fable of the Keys, a paper whose authors seem to have an axe to grind, admit that (full citations for these can be found in the paper):
So there is a speed improvement to the Dvorak keyboard over the QWERTY keyboard. It's just not a very big one.