"Our whole team has a copy of Keyword Researcher, we use it for everyone of our client's keyword research for the 'Long Tail' and we use it every day to come up with blog post ideas and ideas for guest posting. We couldn't live without this tool. I have used every paid keyword research tool under the sun, and this by far is my favorite tool for mining the Long Tail."

Mentioned in the above video is the Keyword Competitiveness (KC) feature within Long Tail Pro. With earlier versions of Long Tail Pro, you could only access this feature if you paid extra to upgrade to the Platinum version of Long Tail Pro. Pricing structures and the way the software is delivered has evolved over the years – and currently (as of the date I am writing this) all features of the software are included no matter which payment plan you choose. So right now – everybody who buys Long Tail Pro has access to this extremely powerful feature.
I also hang out in SEO forums and groups and see KC scores tossed around and talked about and pretty much everybody is on the same page. Most agree that you can’t completely rely on the KC score (there are a few factors that can’t quantitatively be measured with a number) – but that the KC score is a VERY good indicator of the competition level for specific keywords. The following diagram realistically shows exactly what to expect from certain KC scores…

I love Moz’s interface and how they give you data on the keywords. It’s easy-to-read, making it an ideal solution for both experts and newbies alike. They’ll show you both numeric and visual representations of a keyword’s monthly search volume, its opportunity for ranking, priority, and difficulty. They’ll also show you keyword suggestions and SERP analysis, which is fantastic and detailed.
1 – I’ve found a niche with low competition and good CPC . but the thing is the while doing competition analysis. I observed that most of the sites that are in the top 10 serps ranking are small ecommerce site selling their own product or sites like niche specific classified ad site with low and thin content. What are your suggestions ? Should I go for such keywords ?
This tool allows you to type in your keyword phrase or keyword in the field that is provided and it will generate a long list of suggested keywords.  It has three button level and you can perform a deeper search by clicking on button level 2. You will get a list of keywords or keyword phrases that are related to the original list provided in level one. If you want to continue further, you can click on level three and then click the link at the bottom to download the data. The tool can assist you to discover those keywords that your competitors could be ignoring and use those opportunities to create fresh targeted content.

Basically, Google shows the autocomplete suggestions whenever you start typing anything into Google search box. It is in Google's best interest to show the most relevant keywords in the autocomplete suggestions. Keywords that would help Google to retrieve the most relevant websites and help users find the most relevant content for their search query.
We at Moz custom-built the Keyword Explorer tool from the ground up to help streamline and improve how you discover and prioritize keywords. Keyword Explorer provides accurate monthly search volume data, an idea of how difficult it will be to rank for your keyword, estimated click-through rate, and a score representing your potential to rank. It also suggests related keywords for you to research. Because it cuts out a great deal of manual work and is free to try, we recommend starting there.

WordStream for PPC is a full-service PPC management platform for creating, optimizing and managing pay-per-click advertising campaigns in Google AdWords. Our PPC software includes easy-to-use PPC keyword tools, campaign creation and expansion tools, Quality Score optimization tools, and more to help marketers get their PPC work done quickly and cost-effectively. WordStream for PPC customers experience increased traffic and greater ROI.

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).