I'm no expert, but I were going used Manual Trans, I would really think about the extended warranty.
Otherwise, if you can afford to get yourself a new car should yours blow up (minus anything insurance would cover), then you can likely skip the extended warranty and invest the money elsewhere, depending of course on your acceptable level of personal risk.
(In other words, it all depends on you. You could skip it and be one of the 5% with huge issues that make you wish you hadn't gotten it. Or part of the 30% who have zero issues and consider it a waste. Or part of the masses that have a few small things that may or may not cover the cost of the warranty in the first place... It's unpredictable.)