It took me six months to get up to 45 wpm with Dvorak which was much slower than I expected.
The layout was better than QWERTY in some ways: the positioning of 't' and 'h' next to each other works well so I never once typed 'teh'. On the other hand, I missed being able to type 'were' and 'are' and 'here' so easily and I hated the strain of having 's' on my right little finger together with 'l' and the shift key for 'I'. Although Dvorak is meant to be better for RSI my finger got quite sore at times. Plus it's a nuisance faffing around changing the keyboard set-up for different users. So I decided that Dvorak is not right for me.
My QWERTY speed had dropped to 15 wpm but now, less than a fortnight later, I'm back up to 48 wpm.
I don't know if Dvorak is inherently hard to learn, or if I'm too wedded to QWERTY. Maybe it's because I get brain fog from my thyroid problem. I don't know.
I'm not sure if I regret the experiment or not. At least this way I won't wonder about it and now neither will you: I did the experiment so you don't need to. No need to thank me!
(For a completely different view of the attractions of Dvorak, see Holly Lisle.)