I personally believe the economic scare stories are just that. These things find a balance.
Economics and immigration and all that pish aren't really the issue - all things will find a balance - it is the way of things. National sovereignty is really the only issue - you either want it or you don't.
Scotland's geography and lower population density means that certain things cost more than they do in England, which is why Scotland receives more public money than most other 'regions' of the UK.
Scotland as an independent nation would have to find more and better ways to save money and make money.
The Scots are globally renowned as a resourceful and inventive people who have led the world in many areas.
It is not unreasonable to suggest that making enough money to survive and thrive is not outwith the wit of the Scots, but Scotland has social diseases that mean that many are passengers. The shiftless drunks, junkies and lazy bassas who won't get a job will not help. Everyone would need to grab an oar and start rowing.
Scotland has much to offer: IT industries, tourism, food and drink exports - the Scottish brand is recognised around the world as a mark of quality - renewable energy with wind and wave power, currently untapped oil and gas reservoirs... but it would require investment in infrastructure, which would initially mean more borrowing etc. Having just got back from Italy, their inter-city train services are absolutely fabulous. We used trains to get from Rome to Naples and back, Rome to Florence, Florence to Pisa and back, and Florence to Bologna. Comfortable seats in air conditioned trains, running EXACTLY on time, taking people to where they wish to go. How hard is it to do that?
Anyway, fkn rambling again... the fact is that iScotland would have to either spend less or make more, neither of which is an impossibility. It only requires the wit and the will of one of the most resourceful and inventive countries this planet has ever seen.