Arguments for Use of Legitimate Heading Tags

Hi all.  Now that screen readers for the blind are incorporating the ability to navigate a document by headings, I have become a real advocate for proper use of headings rather than just using large or bolded text to create something that looks visually like a heading.  I was discussing the virtues of headings with a web developer in-house who has become pretty enthusiastic about web usability and such.  When I mentioned using real headings and then tailoring them to the developer's desires visually using stylesheets, she said, "Boy, that's going to take a lot of re-work since practically *nobody* uses HTML heading tags." We discussed how small a group blind people were within the company and whether it would be hard to sell folks on starting to use real headings rather than just marking up span tags just to serve that minuscule group.  So, it comes down to this:  I'm wondering who besides screen reader users benefits from the use of real heading tags in documents.  I'd be interested in this group's thoughts.

Thanks,
Jerry