I have no particular disability at the moment and I’m struggling to think of anything that autofocus adds to my browsing experience and not struggling to think of times it’s annoyed me.
On the other hand, I am endlessly annoyed when e.g. Ebay / Amazon do not auto focus the search box on page load. Anything else I'm going to click and probably 50% of the time I want to search. Just auto-focus please.