Learning Dvorak was one of the coolest most mind-fuck things I ever did. It broke me when I learned it, and it took a long time to build my typing speed back up in both it and QWERTY.
Fast forward to today, and having been largely using QWERTY for the last decade. I'm trying out a dactyl keyboard to ease some hand pain, and my brain keeps slipping into Dvorak because the keyboard just feels different.