I've been typing on QWERTY forever and see no reason to change. It's infinitely compatible (I don't have to worry about making DVORAK work on my phone or tablet) and speed is never an issue.
The issue isn't about speed, it's about comfort. Two years later and I can't type any faster than I could before, but typing is a lot more comfortable. The analogy I use is headphones - when you switch from iPod headphones to an audiophile pair, you notice the difference the most when you switch back. When I type Qwerty, I can't help but notice "wow, my hands are moving all over the place".
Edit: I should mention that I accomplish switching by using two-finger hunt-and-peck with Qwerty and touch-typing on Dvorak, which maybe lessens it a bit.
> The issue isn't about speed, it's about comfort.
That's an important point. Sure, (I think I read somewhere that) the touch-typing champion uses Dvorak. However, I don't think that I type any faster after 2 years of Dvorak---I just type more effortlessly. Going back to QWERTY feels like a game of Twister.
It's also optimized for two-handed typing, not screen-tapping, so Dvorak on a phone likely has no improvement over QWERTY. For that you would need something like: http://www.almaden.ibm.com/u/zhai/ATOMIK.htm