However, accessibility has been a central goal since Day One. It would be nice to think that we get some SEO from our accessibility work.
Oh, that's a given. In fact, looking at it from that perspective, you begin to forget about the SEO knowing that what you are doing from the accessibility side is covering the SEO basics and then some.
If your site passes WAI-A validation, Bobby, etc. then there is a good chance that you've covered SEO at the advanced level.