If you can afford the loss, skip it.
Applecare is like other forms of insurance - Apple makes far more from the premiums than it cost to service the computers (even allowing a markup percentage to the stores that sell it).
Any consumer magazinw will tell you that extended warrranties are not the best way to spend money. Over time, if you set aside the various premiums for all the extended warranties you "chose not to buy" into a separate bank account, you'd have enough to pay repairs and still be far ahead.
Problem is, can you afford the loss on any one item, especially at the beginning? If your Mac is critical to you, expensive (replacing a $3000 PB vs a $1000 iBook), and you can't affford to get it replaced, then buy the Applecare, knowing that most buyers will never use it but that you can't afford to not have it.
Don't forget to figure in that a 2 year old $3000 PB is not worth $3000 when it breaks - you could replace it with a used, identical model for $1000 from eBay.
Best insurance advice - get policies with the HIGHEST deductable, to cover MAJOR liability ($200,000 emergency operations, etc) that would otherwise bankrupt you, and pay for the smaller claims out of your own pocket. And skip all extended warranties ($70 to insure a $300 washer, etc.)
Also, if you bought with a credit card, look into whether they have any extra warranty protection. I have a Platinum Visa that gives an extra year for free - that's half the Applecare coverage, for no cost.