KeywordSpy is appropriate for most Internet Market research companies. I would not suggest it for a corporate marketing department unless it's a company with a very larger budget. This is also not a tool for small freelancers even though there is a free option, to get the best benefit of KeywordSpy it's best to use most of its features and options and this can get pricey.
It is lightweight, very efficient and can be integrated in WordPress as well. When organizations want to optimize their content online, Squirrly SEO is probably the best option. It shows you exactly what needs to be improved on your page and makes suggestions. Moreover, the Focus Pages feature scans your pages and provides you with a probability of your ranking for the specific keyword.
Most SEO and market research tools offer what KeywordSpy has but are not as detailed and in one place. Consequently, where you can do everything at KeywordSpy, with other tools you find you have to purchase multiple tools or subscriptions from different providers which also don't integrate with each other. KeywordSpy makes your research easier and more efficient.