@James Craig: I take your point that
??ARIA is primarily meant to solve accessibility problems for web apps (the “˜RIA’ in ARIA) that previously had no way to be made accessible??
Using WAI-ARIA diligently and reporting bugs to improve it is the right way to go for web application developers. (And, for the time being, providing a working alternative for users without ARIA-support, at least for crucial services and information that must be available for everyone.)
Thanks for pointing to the “User Interface Independence for ARIA” W3C proposal. I understand your reservations about the DHTML Style Guide WG keyboard shortcuts. I think the mechanisms you propose are quite elegant: they place the burden on the web app to pick up common user input in a user interface- and platform-independent manner, and to act on these events sensibly. If implemented widely that would remove some of the headaches regarding the predictability of interaction (consequences) that users encounter in web apps.
In my arches metaphor, I took the second arch to to stand for the ensemble of UA and AT, but I agree that three arches would have been better.