As someone who has used Wordtracker on and off for a couple of years now, I thought I give their free FireFox plugin a try to see how it works. It’s actually pretty easy to use and you’ll find it helpful if you’re an active blogger. It works similar to another free tool from Wordtracker, Free Keyword Suggestion Tool.
The FireFox plugin is actually more convenient to use plus it offers functionality that doesn’t work with the Keyword Suggestion Tool. As you can see in the example below, in addition to giving you frequency for the keyword and associated phrases, the bottom half of the panel allows you to track the keyword density for your post.
While this is no substitute for the actual Wordtracker Solution, if you have used the product or similar products and understand the limits you will find it to be an easy to use quick reference tool.
As for the actual Wordtracker tool and other tools similar, they typically give you quite a bit more data like expected search results from other popular search engines, KEI stats, Adword pricing, etc. I have found these tools to be effective beyond doing SEO and Copywriting work. If used in conjunction with other analytical approaches you can use them for market research, new product introduction analysis, and competitive analysis.
As with all things SEO and Interactive Marketing, much of this requires a lot of work, trail and error, and analysis.