For service contracts, I'm undecided for or against. I don't personally pay for the equipment I use, so I don't have a stake in it right now. But thinking about the stuff I do pay personally, like insurance, I usually ask myself three questions:
1) What's the worst that can happen, and do I have cash available to pay for it?
2) Can I cash flow this on a monthly basis, or create my own sinking fund, before I should need to pay out for this?
3) Will paying a monthly bill for the service contract/warranty/insurance bring me more peace of mind than not having it?
If I can cover the worst possible scenario with cash, I don't typically pay for the service. Typically, this isn't an option for me.
If I can work the maintenance into my own monthly budget, I could save some money in the long run. Also, if I don't expect issues for a couple years and can create a sinking fund to cover expenses in two years, I'm making interest on my money sitting in a bank account.
If I *could* financially handle the expenses, but having it "taken care of" helps me focus on other parts of my life, it's worth considering.
In the end, it all depends on how much risk I'm willing to take. I buy life insurance hoping that I'm throwing that money away. I don't like the payments, but I like the peace of mind that my wife and kid will be financially stable should I die unexpectedly. There's a lot of risk there I'm not willing to take. But I don't buy extended warranties on my computer or accessories. I put replacement costs into my monthly budget and hope it doesn't have a catastrophic failure before I've accrued enough to replace it. That is a risk I'm willing to take.