A year ago I tried to use the Dvorak keyboard layout, but later gave up when I needed to type a lot of things and couldn't handle typing at 30 wpm. In order to learn dvorak, I had switch all the keys on my keyboard to match the layout. I was already not looking at the keyboard, but now there was no way for even my peripheral vision to look at the keyboard. I can't say it improved by typing speed that much (maybe 5-10%) but my dependence on seeing the keyboard has been completely removed.
Oh on another note, I recently noticed that I hit the CTRL key (it's a regular keyboard, with the ctrl key on the bottom left, not where the caps lock is) with the knuckle of my left pinky... somehow I started doing this and didn't even notice. Does anyone else do this?