I’d give Long Tail Pro a 4.5/5 stars for its’ ease of use, ability to generate a high number of long tail keyword searches of low to medium competition, check rankings and check Top 10 competition on any keyword search as to what the results of number of backlinks, domain authority/page authority and other pertinent ranking data from Moz.com’s api.
It’s very easy to use, fast and smooth and gives you tons of Long Tail Keywords. You only pay for the web based software once, so there are never any monthly fees. I’ve also been impressed over the years at how easy it is to update. These updates are free and the creator (Clever Gizmos) is always moving with the ever changing world of SEO and updated API’s to keep his program up to speed and fresh.
Long Tail Pro is a keyword research tool that helps you quickly find low competition keywords for your website. In particular, the tool is built for people doing SEO (search engine optimization) as opposed to people doing paid ads (Google Adwords PPC). I'm sure there are some advertisers that use the tool for paid ad keyword research, but the tool was built for SEO keyword research.