Seems to me this clip can't be touted as an accessibility-driven accessible solution until testing shows it is accessible, and doesn't create other problems.
I hope I've worked out that sentence OK, and haven't picked it up wrongly - all I can say is fair enough, I don't think anyone is actually touting it? just thought it was interesting given it does actually pass more "real world" tests than a theoretical test ;) Yes it's more accessible than display, visibilty and text-indent..(seen some those tricks before haven't we?) - but have you seen a better one yet or a real life case which suits everyone? - I know you are anti hidden, so am I really - but working with the CMS's and letting them evolve is very illuminating - the what should be be done (boring "spec" wise) as opposed to the what is actually being used are different things.
I'm not sure that I actually mind which method is the best for both design or the accessible AT world - it just seems clear that this is one area that's very much evolving by itself, and the similarity between user behaviour and "rules" are interesting
I don't see this as an abuse of headers but a very important use of them - I don't for one minute think this is why HTML5 have their "sections" or why Drupal has its "blocks" - it's more a convergence of something that would have happened anyway because it's natural perhaps?.. I like the idea of tabbing - not tab index which should never change but tabbing between headers (headlines) or section(division) headings..