Because I love adding my 2c to old threads, here it is
I went to a Web Standards Group meet up here in Sydney a short while ago where we had Craig Sharkie talk about HTML5, which inevitably brought up some lacking accessibility love. Silvia Pfeifer (http://gingertech.net/) spoke about HTML5 video and also brought up the lack of accessibility of the controls in many browsers/assistive technologies. I do believe she mentioned Mozilla are working on this though (because ultimately it is the browser's responsibility to make sure that controls are made available to the assistive technology.
Also heard Steve Faulkner & Bruce Lawson talk about aria roles (and general HTML5 accessibility), while aria roles aren't implemented properly in a lot of places yet, these are things in the works at the moment.
Regarding headings in HTML5, I tend to think that when they are used in the correct way (probably hgroup aside, though I could see potential uses for it) they could be more helpful. For example, when you have an article listing on a blog, does it really make sense for the article headings to be h2 or h3 inside of the listing page. Probably not.
Of course I understand what people are saying, the headings are supposed to give a document outline. I think at the moment, because we are at the cusp of the technology being adopted, the implementations are a little bit lacking. The current parsing algorithm for it is fairly rudimentary, a new one can't just look at the headings, but also needs to look at the context. And that is what it's all about in the end, the context. The article heading is a h1 for the article in the listing, because in the context of the article, it is the most important heading. In the context of the entire web page, the h1 that appears in the site header (which would likely be the first <header> that is marked with the aria "banner" role) would be the most important.
Slightly Off Topic:
Not sure if Jaws 11 is any better than its predecessor, but 10 isn't all that much to write home about. (and I'm being very nice here).