Because I’m naturally leery of tools, I was very hesitant to make any snap judgments on Long Tail Pro. But after I read the reviews on the product and learned more about its seriously cool developer Spencer Haws, I decided to give it a go and made the $97 purchase. As soon as I started using the tool, I quickly fell in love with these two main features:
Keyword research is an activity you undertake every now and then. If you have a clear definition about the product or service you want to ‘sell’ with your website, you should be able to come up with keywords, related keywords, and even more related keywords to make your awesome website (more) findable. As your product and the market will evolve, your keyword strategy should do the same.
Google Suggest isn’t exactly a tool, but I’ve found that it can be useful for identifying potential keywords. As you type a query on, Google Suggest recommends search queries based on other users’ search activities. These searches are algorithmically determined based on a number of purely objective factors (including popularity of search terms) without human intervention. The Suggest dataset is updated frequently to offer search queries that seem to be trending upwards. This feature is largely one of the reasons that you may see repeat traffic of seemingly long tail keywords. By identifying these long tail keywords and optimizing for them, marketers can capitalize on seemingly obscure keywords with little competition.

Depending on your topic / vertical and your geographic location the search engines may have vastly different search volumes. The tool can only possibly offer approximations. Exact search volumes are hard to find due to vanity searches, click bots, rank checkers, and other forms of automated traffic. Exceptionally valuable search terms may show far greater volume than they actually have due to various competitive commercial forces inflating search volumes due to automated search traffic.
The limit on manual keywords could be higher.  I personally wish we could input 10,000 keywords at a time, instead of 200.  However, I understand the costs that Long Tail Pro has to maintain each time a new manual keyword is input.  Not a deal breaker, I just wish the limit was higher. (To be fair, I don't think most keyword tools have a bulk manual option at all).