I took the option to wing it when I brought by 13" MacBook Pro. Its been 4 months so far and nothing has gone wrong
I wing it with iPods but for a laptop I always get the AppleCare, just because to replace the motherboard is so expensive compared to the price of the extended warranty over the two extra years. Plus just to open the case, an out of warranty diagnosis and repair of anything else can run into big bucks too. We're not all DIY aces...
Actual use: I've only had to use the AppleCare on one of my laptops (a mid-2010 that should have got some frequent flyer miles, gee). However, it was certainly worth every penny I paid, for not only that AppleCare but the ones for a couple previous ones as well, which went unused on those other machines
I have also appreciated and used the extended phone service of AppleCare coverage sometimes on various of my laptops over the years, when I would be considering OS upgrade issues or having problems I was unsure whether software or hardware related.
So you never know... and if you have only owned your MBP for 4 months, you still have almost 8 more in which you can reconsider and get the AppleCare. Any time before your original warranty expires. I've done that sometimes when I just didn't want to shell out the extra at the time I bought the laptop. I put a note on my calendar 11 months past the purchase date, just in case I'd space out my deadline for picking up that extra warranty and the peace of mind I (and my budget) get out of it.