This is an article [theregister.co.uk] in The Register UK [theregister.co.uk].
In it, a vocal critic of the WCAG [w3.org] says that they will, for the most part, be ignored, but that basic accessibility is already a key part of most Web designers' "natural workflow."
For myself, I've never sat down and studied the WCAG from cover to cover, but accessibility is important to me, and I always ensure that my sites validate. Further, I also make efforts to hit a lot of the "optional" points that are usually expressed as "warnings" in WCAG validators.
I consider usability to be my most important priority, and that has always been in line with accessibility. However, in the last few sites I've done, they have started to diverge. This is chiefly because of AJAX, which can drastically increase the usability of a site for normally-enabled people, but can cause havoc with many disabled-assist programs and/or devices.
I must admit, that the last site I've been working on has been quite a challenge, as I need to keep WCAG-AAA validation, degrade well, and support a couple of levels of WML; all the while, adding some nice Web 2.0 "bling."