Dvorak works really well for me. (Though you might want to pick Colemak or Neo2 these days.) I use Dvorak on both my Kinesis Advantage and on 'normal' keyboards like on a laptop.

It's not so much about speed, as about comfort.

My personal experience after switching to Colemak is mostly neutral. Speed is about the same after some training, around 70 WPM. Comfort, maybe improved a bit, but no life changing.

Some people claim that they went from 60 WPM on Qwerty to over 100 WPM on some other newly designed layout, but my experience is clear: if you do it for the speed you will be disappointed.

I'd guess the speed improvement in those cases likely came from learning a better technique, like touch typing and using more of your fingers. Afaik a lot, if not most, of the fastest typists are still on qwerty.

I definitely learned to touch type with Dvorak, because I couldn't look at the keyboard anymore to get help.