Well, Alexa's measure, in the upcoming Alexa toolbar, in particular through the web site traffic. This is quite accurate, can operate there is no need to sweat it. Instead, you should focus on high-level, you can in the results page.
I've seen it..and honestly, I think it's a bit over priced. I personally believe they are doing very minor work and extremely basic SEO analysis for a few hundred bucks. I think you would be better off reading a few articles over SEO and doing it yourself than paying their prices.