To put this in perspective, the independence debate as a result of this pronouncement just moved up a notch into very serious business level and I'm reluctant to make any pronouncements about it because it's so serious. Osborne and Cameron have basically just made a move that will either break us or break them. Only the SNP's response and the next opinion polls will give us the answer as to where this is going to go.
There are two ways this can go, you see. The Tories are going to scare Scots out of voting for independence based on this hardball Dirty Harry bullshit, or they're going to turn Unionist supporters away with their blatant intimidation. I believe most people have a rough idea of what they're going to vote for anyway regardless of an issue as dry and tedious as the currency, but it's more the general hardball tactics the Unionists have been playing in the last week or two that's important.
They're basically trying to get Scotland to take on a share of the national debt, minimise the amount of assets we will receive and forcibly erect border controls to maintain two separate currency zones (unless the SNP start using the pound unofficially like Panama uses the dollar or something) contrary to the interests of the British public. Of course come the Yes vote and the negotiations that will follow they will see things very differently (the question is not "how do we stop Scotland from voting yes" but "what kind of Scotland do we want as a neighbour) but this entire debate has just become a game of very, very high stakes poker.
Regardless of what happens I can't see the Unionists coming out of this well. Even if Scotland votes No based on these tactics, a Union effectively founded on coercion is a Pyrrhic victory for Westminster. They've also potentially overplayed their hand when this would have worked much, much better if they'd suddenly introduced it a few weeks before the referendum or something. To introduce this now with 7 months to go is a bit silly. They've just completely dropped all of their spaghetti over a few successful polls, it remains to be seen what the effect will be though.