Salmond's position is that his first preference would be a formal shared currency. The advisors to the Scottish parliament which included two Nobel Laureates in economics suggested it would be beneficial for both Scotland and the rUK though they gave other options too. So of course others may disagree but it isn't the fairytale thinking that some would suggest. Initially the thought was that Salmond was just thinking of it as a stepping stone. Kirsty Wark on Newsnight tried to get him to suggest he'd commit to it for at least 40 years which he refused to be drawn into it. When the unionist parties came out with the "it's not going to happen" without really any apparent consultation some in the Yes campaign suggested it was a campaign strategy more than a serious response to the idea and that it would at least be discussed should there be a Yes vote. The No campaigns problem though is that they've thought various things, including this one, were game changers but of course they haven't been. The main driving force is that many people feel that only controlling our own destiny will in the long run enable us to build the type of society and nation we want - so despite the barage of "we love you but wouldn't work with you" coming from Westminster the polls have still been closing. Of course should there be a currency union then financially Scotland would be constrained by economic rules etc and they would have only a voice on the BofE and wouldn't control much - but of course at the moment we have no control anyway and the Scottish gvt has no voice. Many people feel that the big matters are being controlled by a gvt which has no real mandate to do so. On many other matters an independent Scotland would have far more control over its destiny than it has at the moment.