Using the good ol' free Google Keyword Planner is great. But there is an alternate universe of Long Tail keyword phrases that live in Google's other database--namely, their "Autocomplete database." That's the database that is accessed when you're typing queries into the Google search box (notice that list of suggested keywords that pop up as you type?)
One of the most important aspects of an effective SEO strategy is the ability to research, analyze, and ultimately select the keywords that are most likely to result in success for your clients. There are a variety of free tools available on the web specifically designed to help online marketers do just this. Each tool has its own unique methodology for collecting and presenting this data. Comparing any of the tools’ results without knowing the subtle differences can lead to incorrect inferences and an SEO strategy based on misinformation.
It would be great if you can provide comparative analysis of this tool with Google Keyword Planner. Since you’re using this tool so you can provide best comparison. One differentiation which I understood is that this tool works for yahoo and bing as well whereas Google keyword planner works only for Google but Google being a dominating search engine, gives the highest returns, so only this reason may not be enough to buy it.