Food for thought.
You can of course use whatever layout you like and then while ctrl/alt/meta is pressed it switches to qwerty, doesn't save vim users though (or other applications where shortcuts don't need to be prefixed).
I'm not convinced switching from qwerty is that beneficial, I believe (but have not yet tried it) an orthogonal keyboard will do more than any layout will. But I admit that I don't have experience to back that up.
Two minor problems, though: In Dvorak, V is immediately beside W. Ctrl+V means paste, but Ctrl+W means close window, so care is needed. And, any keyboard that lack Right Ctrl (e.g. the Microsoft Surface series) is an abomination.
Optimizing your layout for English is not necessarily ideal for anyone writing in more than one language.
edit: I guess the above can be manageable (with compromises), but in my opinion it does take away much of the appeal with a new layout.
