I suspect that any time I would spend learning Dvorak would be better spent in figuring out how to get through life by doing less typing in the first place.
In theory, I could argue against the Kinesis in the same terms, but the investment required to come up to speed on the Kinesis is smaller (just a couple of days in my case). And many of its ergonomic advantages -- hands further apart, wrists at better angles, better use of the thumbs, less stretch for the pinkies because their keys are physically closer to them -- are unachievable with any other keyboard, no matter which keymap you use. I would certainly recommend trying a Kinesis before learning Dvorak -- if you're dead set on becoming the smoothest keyboarder in the world, there's no reason not to use both.
Is it just a belief or do you have some reasons?