I switched to the Dvorak keyboard about a month ago. My original post on the transition is here.
My typing speed has increased to a little over 40 words per minute since then. I still make a fair amount of errors, most of them a result of my muscle memory reverting back to the QWERTY layout when I get tired or lose my concentration.
My fingers are finding the keys more and more out of reflex now, though it still takes a low level of concentration to keep them moving smoothly and consistently. I don't notice this much when I'm typing from a script, as that doesn't require me to split my attention. I'm sometimes able to get enough of a flow going to where I hit the "autopilot" threshold, where the active brain is able to take a step back and "watch" the magic unfold. That's a wonderful feeling that I remember well from the times when I would start to master a difficult passage on my trumpet.
Just as with my trumpet, however, that magic is revealed as a cheap illusion when even a few brain cycles are required for something else. When I compose a blog post, for example, or send a chat message to a friend, and have to think about what I'm typing instead of mindlessly mimicking the letters in front of me, things can fall apart rather quickly. That's when it becomes obvious, sometimes frustratingly obvious, that the typing is taking more concentration than I realize.
This is compounded by the fact that I think in words, but still type only letter at a time. This extra layer of "translation," from words to letters, burns even more CPU cycles and gums up the works even more. I'm making progress with this. I'm seeing more and more instances where smaller words -- and, the, etc. -- have become part of vocabulary of words which are able to make their way from thought to screen without all the apparent mental gymnastics. It's kind of a fascinating process.