I bought the stickers for my home only because if I left the layout in DVORAK (as I usually do), then my wife wouldn't be able to login. Or, at least, that was true when I made the switch. Now most lock screens have an easy way to switch layouts.
At work and with my personal laptop (that isn't shared), I do not use the stickers because it prevents me from looking at the keyboard. Plus, when I do look down and see the stickers, I see white-letters and blue-letters. It makes it more confusing which key I am about to press. I end up mixing up words between DVORAK and QWERTY regardless of layout.
I switched to the Dvorak keyboard about 5 years ago. Previously, I typed 110 WPM on QWERTY, and while learning Dvorak my WPM rose quickly from 10 to 70 WPM, but remained there. I now type at about 80 WPM, but even with practice I have not been able to regain my previous speed. I can switch to Qwerty, but my WPM has gone down too -- it's about 80 WPM now.
I realized that I had been achieving 110 WPM because I had unconventional hand positions (I never learned to type "correctly", so it just developed). Learning and staying with the "correct" hand positions brought down my WPM. Previously, my hands flew around the keyboard, but now they're mostly stationary on the home row. The positive outcome of this is that I can now use non-traditional keyboards such as the Kinesis, where I cannot move my hands around while typing.
I don't regret going to Dvorak because of the great comfort it brings to my tired hands, but I do miss the speed from time to time.
I don't know that I manage more than a sentence a minute - the limiting factor there isn't my typing speed, it's thinking through and editing what I'm going to say. Programming, it's probably on the order of 10-15 characters a line, and unless I'm doing mindless boilerplate, that line takes a minute or two to think through.