Mac OS X (like Mac OS 9 before it) has a special keyboard layout
called "Dvorak-Qwerty" available in the International control panel.
It works just like the regular Dvorak layout, except that when you
hold down the Command key, it rearranges to QWERTY - that way, you can
use Dvorak for all your ordinary typing, but your muscle-memory
shortcuts like Cmd-Q and Cmd-W remain unaffected.
When I set up a mapping in MacVim like:
nmap <special> <D-e> :echo "foo"<CR>
...I would expect to have to press Command plus the key labelled "E"
to trigger it (even though that key produces "." in Dvorak. It turns
out I have to press Command plus the key labelled "D" (which is the
key that produces "e" in Dvorak).
Interestingly, shortcuts that appear in menus (such as <D-T> for New
Tab) work fine.
On a related note, it seems that while you can map either "<C-E>" or
"<C-e>" equivalently, it seems that trying to map <D-E> doesn't work