SEO Book's new Competitive Research Tool looks pretty darn good.
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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.