For frak's sake, buy it!
Always, always, always buy applecare for any apple product, especially a portable. If something goes wrong with it, they're especially difficult and expensive to repair. If a logicboard dies 13 months after you've bought it, it's almost as expensive to replace it as it is to buy a new computer.
You also get apple phone support for your product for three years, and it will cover many apple peripherals like keyboards and mice.
You can save a bit if you buy it off of ebay, just make sure it's a trusted seller and they send you an unopened box.
If you decide to sell your machine and get a new one, the fact that it's covered under applecare will make it more likely to sell and increase its value.