- how the on page optimization of any page looks (headings, meta description, page title)
- the keyword density of the page and popular phrases on the page
- how many links point into a page (total links, or links from external resources)
- how many links point out of a page (as well as the anchor text of these links, nofollow vs follow, internal vs external - all exportable in CSV format)
then this new feature makes it quick and easy to do all of that. Simply right click on the page you are viewing, scroll down to SEO for Firefox, and click on SEO X-ray.