The device was first mentioned in a full-page advertisement in The Economist in August 2006. Various media outlets mentioned it - such claims usually get mentioned every few years. However, there is a long history of such machines, and none of them has stood up to a test.
Over the past decade or two, the term "perpetual motion" has been replaced by "over unity device", but the story remains the same.
Some, such as Paul Story, have blogged in support of Steorn. Paul Story himself says he bases his belief on how much of a risk the company is taking on being wrong. This was incredibly naive of him - many people have taken huge risks and lost much - think of tulip mania. Mr. Story also is a member of the Steorn Private Development Club, and though he claims that he has an open mind, he lets his excitement slip with comments on how the technology will change humanity. Unfortunately, it looks like Paul Story has invested emotionally as well as financially and this may skew his views.
Professor Eric Ash is quoted on tech.blorge.com as saying that "I believe that Mr McCarthy is truly convinced of the validity of his invention. It is, in my view, a case of prolonged self deception." - in other words, McCarthy was honest, but fooled himself. Paul Story still believes.