I switched to Dvorak in 2009 for touch typing on a full-sized keyboard (IBM Model M). When I got my first smartphone (Nexus 4), I used a Dvorak keyboard layout for quite a while, but I found that the arrangement of the Dvorak layout, so ideal for touch typing, actually made two-thumb typing a bit tougher than QWERTY on a small mobile device. I switched back to QWERTY on mobile permanently when I first got access to a swiping keyboard, because there's less ambiguity per pattern (since common letters are spaced further apart).