The Not Voting Question

A question i have been asked frequently and more so as the election looms is the one that Russell Brand received a bit of a bashing for, 'Is it okay not to vote?'
The first taste many 18 year old's got of voting at the last election was boosting the Liberal Democrat vote after they made a solemn promise not to increase the student fees and then finding the party did exactly that when they joined the coalition and supported the Conservatives tripling their tuition fees. Obviously that was duly noted and also by the generation of students that followed who now find themselves tens of thousands of pounds in debt at the end of their courses and the Lib Dem's can fully expect to be horribly decimated this time around.
That sort of experience is obviously going to sour a voters view, they rightly feel cheated and lied to and so look elsewhere to place their X on the ballot paper.
What if after taking a look around at the other parties and decide that you don't like what any of them are offering? Should you hold your nose and vote for the 'least worst' option, the one that you disagree with the least, or withhold your vote from all of them as a recognition that you would not be happy to endorse any of those on offer.
There is no option on the ballot to state 'none of the above' but you can spoil your ballot paper by writing it on there or crossing all the parties out but the party with the most votes is still going to get into power. 
My personal view is if you have looked into what all the parties offer and you do not find one that chimes with your beliefs then it is a perfectly legitimate strategy to not vote but it would be better to actively spoil your paper and write in 'None of the Above' as spoilt papers are counted and if significant numbers of people vote for nobody and state they feel unrepresented it will become a news story as it cannot be dismissed as voter apathy or people just not bothering to vote and hopefully would send a signal to the political parties that they are out of touch with a large number of voters.
The swing side of that of course is that you are not voting against the current ruling party so you are not registering your choice to remove them from power, therefore endorsing them in a backhanded way to carry on running the country so give it some thought before May and you find yourself (or not) in the polling booth as it's a tough choice.