I pretty much gave up and bought the "Creating Flow with OmniFocus" ebook from here.
http://www.usingomnifocus.com/
Or read the free articles from:
http://simplicitybliss.tumblr.com/tagged/omnifocus
http://www.asianefficiency.com/omnifocus/
It was definitely worth every penny. Sometimes third party authors offer a different perspective and provides new tips and workflows that can't be adequately in an official manual. Oftentimes, I find official manuals more as reference and doesn't really shine a spotlight on different workflows.