KW Finder is similar to the Google Adwords tool; it even pulls up similar results, which aren’t as entirely on-point as the immediate results from SEMrush and Moz. From my experience with KW Finder, the searches are a lot better if you put some time into manually adding in filters like negative keywords and additional keywords you do want to include.
But it’s still very useful for getting search volume data (provided your account still shows this), which is helpful when choosing which of the many keywords you’ve found to focus on (although you should take these estimates with a pinch of salt, they are still useful in indicating the relative search volumes of different keywords, even if the absolute estimates are a little off).

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).
I ditto what you are saying. All of the keyword volume data the system is stating is completely way off, false and misleading. They are pulling these numbers now from 3rd party sources, which we all know are directional, but in many cases in left field! I just signed up and will probably be cancelling because I can’t trust or rely on their data. What a shame, because before it was such a great tool.

In a nutshell, Long Tail Pro helps you quickly find keywords in bulk based on a seed keyword that you input.  In addition to returning hundreds of related keywords, the tool also shows search volume (monthly search volume), advertiser bid, number of words, rank value, and my favorite Keyword Competitiveness (helps you judge the competition and keyword difficulty).