This is one place where I found myself to differ with Apple's usually brilliant UI norms. Trouble with this particular guideline is that it makes me (as the user) have to read and process the responses in my mind, making response slower. A Cancel/No/Yes with a question "Save and quit?" makes the same sense to me and allows me, to process the known buttons almost reflexively.
The problem with Yes/No/Cancel is it requires the user to look at the question which can often be the opposite of what the user expects. Example
Save? Yes/No
Delete? Yes/No
Overwrite? Yes/No
Those all have very different meanings when answering "Yes" where as when you put the meaning on the button the button has meaning all by itself. No need to look at the description above it.
That's a good point. There's a cash machine near me with a trick question:
'Are you sure you wish to continue without a receipt?' Yes/No
I have several times just seen the word 'receipt' and instinctively hit No (because I don't want a receipt). This cancels the process and spits my card out and I have to start over. Annoying.
But then perhaps that's more an argument against badly worded questions. This is a Santander ATM (Spanish company) so I do wonder if it's a poor translation (or perhaps that is just the standard phrasing for all ATMs in that country).
Generally speaking I'd agree that if you keep your questions simple, then Yes/No buttons are quicker to mentally process. Most cash machines simply ask: 'Would you like a receipt?' and my 'No' instinct is the correct one.
