Nope. I still type Dvorak. One switch is enough.

I can type QWERTY, too. If I use a different machine, I'm able to switch over with surprisingly few errors. Also, strangely, I can't tell you where the keys are on a Dvorak layout without mentally typing the letter. I used to know the QWERTY layout by heart, but never reached the same level of mental mastery with Dvorak.

The only reason I suggest Colemak is that I've heard it's optimal for programming. I still don't think it's worth learning, though, if you already touch-type QWERTY.