I think it would be safe to assume that if it is still important then it is gradually diminishing in importance because positioning and layout don't necessarily equate to quality content.
That said, recent algo updates relating to above the fold advertising and page-load times clearly mean they impact in one way or another. And I think how you link elsewhere also has an indirect impact in terms of relaying how you view a page's importance.
So yes I think it matters but only where the impact has a knock-on effect. I personally don't think coding and positioning of divs, tables etc or even H tags are so important anymore but it makes sense to develop cleanly and logically and I must admit I still try to develop in a logical layout, more through habit than anything SEO-related though.
I red somewhere that Google will penalize pages which have lot of rubbish on the top of the page. Rubbish means big ads, multiple ads, many external links or anything, that pushes the actual content of the site down out of sight (so you have to scroll page to get to content).
You may find this tool useful: Browser Size Labs [browsersize.googlelabs.com]. While it is designed primarily for what site visitors see, it does help with SEO as you can easily see important areas. I did see a notice on the page that they will be doing away with it and putting it in analytics, though no date was specified.