Well, I rarely type English text of any length when playing Dwarf Fortress, and don't see any benefit of the Dvorak layout.
Although reducing hand movement for the language you're using seems a far more sensible design goal for a computer keyboard than keeping a mechanical typewriter from jamming.
When it comes to keyboard layouts, the fastest is what you're used to. If you want to spend the time and effort to adopt a new keyboard design, unlearning what muscle-memory you have in order to then gain a few tenths or hundredths of seconds in subsequent typing, fair enough. (I'm sticking to QWERTY, but I've been tempted by one or other of the "hand-typer"/stenography input devices, in the past.)
The main problem with switching, however, is that of the logical (or, as others may think,
illogical) non-cursor direction/resize keys such as UHKM needing to be remapped by the end-user to suit a similar combination that works well with their layout (and doesn't clash, or can be made not to clash by further remapping, with other keys active at that time).
Anyway, my Dad has a programmable Casio calculator with a full alphabetical keyboard, in alphabetical order. Horrible to type on. Not because of the lack of reduced finger movement, but because even though I know the alphabet backwards most of the time is spent trying to work out where to send my fingers in the first place. As a not-quite-a-touch-typist who never learnt the "home keys" method but sends the hands and whichever terminating digit is most handily available to the right key-top 99 times out of 100 (save for when I manage to djogy yjr jsmfd pbrt nu pmr[1], for an entire sentence or two) I'm happy with QWERTY.
But this has no bearing on DF, given that speed is not an issue. I've said it before, and I'll say it again, that you can always pause and think, or reverse (most) bad selections. I'd already brought up the "delete this burrow" problem, which probably happens
because I'm such a fast and innate (if not 'inane') typist.
Anyway, that's about the only thing I agree with KurzedMetal about, as should be obvious to anyone having painfully read everything I've posted here.
[1] "shift the the keys over by one"