Yes, they have been subsidised for years by the southerners and we have had to endure decades of wasteful misrule under Labour governments that only got elected because of their Scottish MPs. That's why they have continued to pump English money into their economy.
Then there is the Shetland Islanders' attitude to independence to consider.
http://www.telegraph.co.uk/news/uknews/scotland/9794316/Alex-Salmond-warning-over-Shetland-oil-after-independence.html
http://www.guardian.co.uk/uk/scotland-blog/2012/mar/19/islanders-threaten-salmond-independence-plans