Tests: Jason Kiss tests accessible ARIA, tree widgets in mutliple SRs.
He shows that right now, there are various differences between browsers and AT's handling of ARIA in trees, so it's not very stable right now. But he does have a best-choice example which bascially works with current browsers and screen readers.
In my opinion, VoiceOver not keeping the cursor in check with keyboard cursor and moving tabIndexes is indeed a bug. I would think this, combined with webkit's in-page link bug would make thing pretty hair-pulling for Mac users.
Good work Jason.