SEO Book’s new Competitive Research Tool looks pretty darn good.
The main advantage of it I can see is that it shows the positioning of your SEO competitor for each individual keyword. This makes it very easy to tell where the SEO keyword opportunities/openings are.
I’m already imagining easy-to-make Excel charts with a column for the keyword, and the search engine positioning of every competitor. We already do this at MB, but this tool will make the creation of such a chart much, much easier.