A lot of people "forget" that an independent Scotland wouldn't necessarily be the version that Alex Salmond wants - there's a risk that a lot of voters will be turned off by thinking that voting "YES" means voting for the SNP's policies on tax/ spending/ environment/ nuclear/ transport/ whatever. I think that the "YES" camp would do better by reminding people that an independent Scotland would be free to make its own mind up about things like cutting Corporation Tax (which seems to be an SNP policy), rather than the "any colour you want, as long as its Salmon Pink" version.
(and, just like an independent Scotland isn't necessarily going to be an Alex Salmond dominated one, a United Kingdom isn't necessarily going to be a David Cameron dominated one - he won't be around forever)
Anyhow, this isn't a general thread about independence (would Scotland be a "new country" in terms of EU membership etc etc), this is a thread about a currency union ("getting divorced but keeping a joint bank account") on a railway forum.
So, I'll suggest a railway related comparison. Ever since they privatised the railway, the Government have gained more and more power over the railway (much easier to hold private companies to task than unaccountable British Rail). There's a danger that an independent Scotland will see "London" (i.e. that nasty Mr Cameron and that nasty Mr Osbourne, two rather unpopular chaps north of the border) having more control/ influence over the Scottish economy than they currently have.
At the moment, the Bank of England sets Interest Rates for the good of the UK overall (including concerns about Scottish jobs, Scottish inflation, Scottish prosperity). If Scotland were to leave the UK then decisions would be taken in the interest of the remaining bits, with no Scottish representation and no accountability to Scots. Be careful what you wish for.