I also think it’s a little vague for actually basing niche research off of (sometimes their green bar implies that a topic might be fairly popular, but it turns out it gets 100 searches a month or something pretty low), and I like http://www.keyworddiscovery.com/search.html for harder numbers.

I’ve never paid for keyword research tools though. I’m sure the paid ones give you a lot of good information, but I’ve found the basics to be enough in confirming whether or not a niche is a good one (a lot of times, it’s just a matter of using common sense: i.e. products with higher profit margins can pay affiliates more or–if you’re selling them yourself–put more in your pocket).