Be sure to re-evaluate these keywords every few months -- once a quarter is a good benchmark, but some businesses like to do it even more often than that. As you gain even more authority in the SERPs, you'll find that you can add more and more keywords to your lists to tackle as you work on maintaining your current presence, and then growing in new areas on top of that.
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.