you know what i would love? a tool by Google that tells you what they think of your site. if you're doing anything wrong that they are punishing you for or something. does such a tool exist?
What about Google Webmaster Tools: http://www.google.com/webmasters/tools/
Once you verify that you're the proper owner of the site, it gives a bunch of information about how well your site is indexed, ranked, if there were errors with the crawling, etc.
They punish people for trying to game the system. Just make a good website, try to be the best at what you do, be consistent in your publishing and Google will reward you.
Getting good traffic to a website is not hard. Getting them to buy is hard.