I'm surprise at Shutterbug for allowing such a misrepresentation in this article here and in print (August 2011 issue). The "Canon Extender EF 2X III" is not completely compatible with the Canon EF 70-300mm f 4-5.6L IS USM lens. In order to attach the extender you have to set the lens at 300mm and then it becomes a fix 600mm focal length. Joe Farace had to have known this and should have stated so in the article.
Not everyone who reads Shutterbug is a Professional or a long time experience photographer. I was trusting Shutterbug to give me insight into becoming a better photographer without wasting my money. Your article led me to believe I would get a 140-600mm focal length range by using the Extender. I shelled out $500 for this extender based on this article. I will never trust Shutterbug again