I've used QWERTY for most of my life, but then I had a Repetitive Stress Injury in my wrists, hands, and forearms. I tried learning Dvorak because I read that it required less stressful hand movements, but I just couldn't make the new layout stick in my mind.
Then, I came across an online test. You entered something typical that you had typed (I entered one of my blog posts) and the text was analyzed and the best layout recommended. My results were the Colemak layout. So, I tried learning that, and it was easier than Dvorak. I've been using Colemak for the past three years now. I can't type quite as fast as I could with QWERTY, but it's reasonably close, and I can't remember QWERTY anymore anyhow.