Qwerty was good in the late 1800s when people used typewriters and the keys were laid out in alphabetical order, causing frequent jams of moving parts. But with the invention of electrical typewriter in 1930's which used a ball to type letters rather then moving arms, an opportunity arose to redesign keyboard layout to improve typing efficiency. Enter Dvorak!
Benefits to learning the Dvorak keyboard:
Increased comfort - (the top reason for typist suffering with RSI)
Increased efficiency
Better accuracy
Faster
Shorter learning curve (estimated 50% shorter then Qwerty)
Arguments against Dvorak:
Dvorak keyboards are expensive - Computers come with free Dvorak software installed and all you need to do is switch in Control Panel.
I'll have to retrain myself! - You will, but your kids won't!